Buy Roku 3 if you want voice search on your remote (rather than by downloading an app on your phone), you want headphones, or you want to pick from a few simple games. Otherwise, buy Roku 2. Roku 1 also has 1080p (HD) resolution, but the processor is much slower. Only buy Roku 1 if you don’t mind a slower user interface and other delays.
https://www.amazon.com/Roku-Streaming-Player-4210R-Processor/dp/B00UJ3IREE