As mentioned in the OP, I'm pretty evenly split between the Chromecast and a Roku 2 XS. From my perspective:
- Chromecast
- Pros
- I love the ability to cast stuff from my phone. The interfaces are usually way quicker and the on-screen keyboard is much better than tap tap tap tap tap on other devices.
- Screen casting (either from phone or PC) is a nice backup for media that won't otherwise work.
- At $30 a pop, you can load up every TV in your house with them for the cost of one Roku 3 (though the Stick works fine as well).
- Cons
- It seems to be a little finicky when it comes to connectivity. Sometimes, a Chromecast device just won't show up as being available.
- Amazon hates Google, so there's not really a good way to do Prime Instant Video.
- Roku
- Pros
- Not tied to any ecosystem, so seems to have the most support of any of the options.
- You can at least use your phone as a control, so you can technically use a phone keyboard to control it, though it's not great.
- I don't have to explain how to use it when guests visit.
- Cons
- Seems like the apps don't get updated as fast as the Chromecast apps do since the latter are really just phone apps.