We will compare the Roku box, the Apple TV box, the Google Chromecast stick, and the Amazon Fire TV Stick. Personally, the ideal streaming device will be compatible with my current subscriptions (Netflix, Amazon Prime Video, and HBO Now), my purchased digital media (iTunes, Google Play, and Amazon Video/MP3), free network streaming (Watch ABC, the History Channel, etc.), as well as relatively obscure media sources. Of course, the ideal streaming device (of our four options), short of being a personal computer, does not exist.
If I recall correctly, Roku's lineup of streaming boxes became popular as Netflix began its Internet video streaming service. I bought one of the first Roku models right before I started my Netflix subscription, about five years ago. My most recent Roku purchase was back in 2012, so maybe the most current box model (or stick model) has more functionality. In any case, with my Roku box(es), I can watch Netflix, Amazon Video (purchased and Prime), the History Channel (for Vikings), and relatively obscure, niche media, like denomination-specific religious programming. I've recently read that Google Play is available for the latest Roku products, but I haven't tried it out yet. I don't know if there is a Watch ABC app for Roku (for ABC's Marvel Cinematic Universe shows, of course).
Currently, HBO Now is only available for Apple iOS devices and personal computers (via browser, after having signed up on an iOS device), so Roku does not have HBO Now. Without the use of an external personal computer, and some fancy know-how, I don't think the Roku has immediate access to my iTunes account, either. These are a small amount of negatives for an otherwise solid line of products. Right now, the HBO and Apple stuff can be covered by ...
In October of 2014, I mistakenly purchased a $25 Apple Store gift card, thinking it was an iTunes gift card. It was a silly lesson learned, with an otherwise useless, nice-looking gift card as a reminder of the silly lesson learned. Earlier this year, when Apple announced the Apple Watch and various upgraded products, they also lowered the price of the Apple TV to $69. When HBO announced the HBO Now service would be initially available to iOS devices and the Apple TV, I decided to take the plunge, use that pretty gift card, and spend an additional $44 on an Apple TV box. I am currently enjoying my first month (free) of HBO Now, with the latest season of Game of Thrones and other cool TV/film surprises.
Being an Apple product, the Apple TV can access all my iTunes purchases, videos and music, in the cloud. Admittedly, my past purchases of episodes of Lost and Supernatural are available on Netflix. I recently watched Up again, and it was as sad and funny as ever. Listening to music through TV speakers isn't ideal, so half of Apple TV's iTunes capability is a bit of a novelty.
Speaking of Netflix, like the Roku, Apple TV can stream Netflix. On the Roku, or at least my obsolete models, you have to search for various channel apps, then "install" them to the device. On Apple TV, it seems that all approved apps are already available to access from the get-go. In effect, Netflix, HBO Now, History, and Watch ABC are all available, and everything is awesome. Almost.
Apple TV doesn't seem to have either Amazon Video or Google Play, let alone any niche media. Most of these issues can be immediately rectified if one has an iOS (or latest Mac) device with AirPlay. I tried AirPlay with an iPad and Apple TV, and they pair beautifully. The potential for big screen TV Skype and/or FaceTime is fantastic.
With an old Roku box and a brand-new Apple TV, I have all my preferences covered, basically. Well, I'll have to see if the Google Play on Roku is a real option for me. If so, it seems the next two devices, both streaming sticks, are varying degrees of redundant.
I arbitrarily purchased the $35 Google Chromecast in early 2014. It's a curious device that requires a smartphone or tablet with the Chromecast app. For instance, a smartphone with the Netflix and Chromecast apps can "cast" the movie onto a TV with a Chromecast stick. The stick will do most of the processing, preserving the phone's battery life. As long as a smartphone/tablet app is compatible with the Chromecast app, you should, in theory, be able to stream that bit of media onto your TV. I haven't tested it yet, but Amazon Video might possibly be finally available for Android smartphones/tablets and therefore potentially Chromecast-able. Both Amazon Video and Chromecast apps are available for iOS devices, but whether they can play well together is unknown (to me, at least).
I think the Chromecast shines best as a YouTube-on-TV device. Both Roku and Apple TV have YouTube, but it is a pain to search for YouTube videos with a remote control. It's as slow as typing out a password on a game controller for an old school Nintendo game, like Simon's Quest. The smartphone/Chromecast combo will allow the viewer to search quickly on the smartphone's virtual keyboard, then shoot the streaming video over to the TV. It's fast, and it's fun.
As stated earlier, Roku and Apple TV cover my media consumption preferences. The Chromecast, while a bit redundant, is icing on the cake with its smarphone-plus-YouTube ease of use. This renders our final device as the odd one out.
AMAZON FIRE TV (STICK)
For a short period of time in late 2014, Amazon sold the Amazon Fire TV Stick for $20, 50% off its usual price. I knew this device would be redundant, but at that price, I had to buy it, just to try it. Because it was a redundant device, I finally got around to opening it a couple of months ago, in early 2015.
If Amazon developed this device years earlier, perhaps it would have been as good as the Roku. History is on Roku's side, especially when it comes to niche media channels. Perhaps Amazon Fire TV might catch up one day. I really haven't explored the Fire TV as much as I should, but it definitely covers the basics -- Netflix and Amazon Video. Of course, much of the interface's real estate is dedicated to Amazon Video. Netflix is an app that you have to find and install. My Amazon Music library (purchased and Prime) is also available for streaming via Fire TV. My Roku has that capability, in theory, but its lack of RAM or some hardware deficiency defeats the potential. Then again, music through tiny TV speakers is not ideal. Amazon Echo does a better job with Amazon Music.
I can't say for sure, but there's probably a good chance that free network streaming apps, like History and Watch ABC, are available for Fire TV. I'm sure that iTunes isn't a possibility, since Fire TV is not an Apple product. You'd have to be an tech wizard to have Google Play on Fire TV, in some sort of roundabout way.
Amazon Fire TV has a "casting" function similar to the Chromecast and Apple's AirPlay. It's called Miracast, and it is available for Fire smartphones/Kindle HDX tablets, as well as Android tablets/smartphones. I tried to pair a late 2013 Kindle Fire HDX with a Fire TV Stick, and it worked ... eventually. It was a slow pairing process; perhaps an up-to-date Kindle and a Fire TV box might have done a faster job. An Android smartphone pairs with a Chromecast more quickly, as does the combination of an iPad with Apple TV.
All of the four streaming devices are Netflix-ready. None of the devices have all the functions I want. Depending on your own streaming media preferences, one device could be enough, and that one device is a toss-up between Roku and Apple TV. If you just want to stream Netflix, then it's a toss-up among all four options, as long as you have a smartphone/tablet for Chromecast. If you don't have a tablet or smartphone, then Chromecast is not for you.
For me, both the Roku and Apple TV are necessary, with Chromecast as a fun addition. Alternatively, an iOS device combined with Apple TV would render the Chromecast redundant. Amazon Fire TV can't compete with Roku's niche channels, Apple TV's HBO Now, or Chromecast's smartphone-required simplicity. If your media consumption tastes are similar to mine, then you'll need at least two streaming devices, possibly including a smartphone/tablet, for your streaming needs. Here's the TL;DR (too long; didn't read) rundown:
(Keep in mind that the Google Chromecast requires a smartphone or tablet with the Chromecast app installed, to actually stream media.)
Roku + Apple TV = Better than good enough.
Roku + Apple TV + Google Chromecast = Ideal.
Roku + Apple TV + iOS device to AirPlay YouTube, etc. = Ideal, fewer devices required.
Roku + Apple TV + iOS device to AirPlay + Google Chromecast = Ideal, but a bit redundant.
Roku + Apple TV + Amazon Fire TV + Amazon Kindle Fire HDX or Android device = Almost ideal, but Miracast seems slow.
Roku + Google Chromecast = No HBO Now (but perhaps in the future), no iTunes.
Roku + Amazon Fire TV = Redundant, no HBO How, no iTunes.
Apple TV + Google Chromecast = If Amazon Video is Chromecast-able, then almost good enough.
Apple TV + iOS device to AirPlay Amazon Video = Good enough.
Apple TV + iOS device to AirPlay Amazon Video + Chromecast = A bit redundant.
Apple TV + Amazon Fire TV = Almost good enough.
Apple TV + iOS device to AirPlay Amazon Video + Amazon Fire TV = A bit redundant.
Apple TV + Amazon Fire TV + Amazon Kindle Fire HDX or Android device = Almost good enough, but Miracast seems slow.
Google Chromecast + Amazon Fire TV = Not enough features, and redundant.
Amazon Fire TV + Amazon Kindle Fire HDX = No HBO Now, no iTunes, mysterious status of Google Play, and fewer niche channel options.
That pretty much covers as much as I can cover, as confusingly as possible. If you have a tax refund, remember that you overpaid your taxes at the beginning of the year. Since you have your money back, go ahead and buy stuff you don't need. Or food and shelter. Whatever you choose.