We have a Roku 1 and a Roku 3, and they are both great for the price. The $50 Roku 1 is attached to an old but "too good to throw away" Sony Trinitron CRT, and the Roku 3 is on our bedroom TV, a 27" Vizio LCD. They both stream via WiFi with no issues (480p on the 1, 1080p on the 3).

I did have a couple of RasPis running OSMC before we went with the Roku devices, and apart from issues with the initial setup, the Pis worked great. The Roku does offer a greater selection of services so there's a lot more 3rd party streaming content available there, and the official Plex app on Roku makes it easier to stream from our media server than the Pi, but if you know what you're doing you can enable uPnP on OSMC and local streaming mostly works fine. You can also run emulators on the Pi on top of OSMC, which is great for nostalgic gaming. The Roku 3 has a limited selection of games and a Wiimote-like remote, but no support for emulation that I'm aware of.

XBian is a small, fast and lightweight media center distribution for the Raspberry Pi, CuBox-i, Hummingboard and many more devices to come. It is based on a minimal Debian and therefore offers much of the same freedom as Debian offers.

Very simple to install and get running.