I have both, the ROKU streaming stick and ROKU 3 on the same home network. As I would expect, ROKU 3 performs much faster, video is less choppy than on the streaming stick.
The Roku streaming stick resembles a memory stick and has a micro USB charging cable a power adapter and remote control. It packs a ton of apps into a compact device that lives behind your TV and is very low cost. The only annoyance is that the remote losses connectivity sometimes and it has to be reset more than I like to but in all a great product and I'm pleased with it.
I was leery of the stick and wanted the player but went with the stick for various reasons. I'm not sorry I did! I love it!
It works well, easy to use, though the menus are different than the classic, with no problems when it comes to storage for channels. It has very little problems with my sometimes touchy wifi connection and doesn't glitch. The only issue is the remote can be a tad tetchy about plenty sometimes.
All I do is movie channels and want the ones offered by the Roku, something that leaves competitors in the dust, so I'm quite happy with the stick. It's better than the standard player, IMO.