Same service, same number of channels. The remote does not come with a headphone port like the 2 & 3 do. Also, the 3 is the only one that is designed to allow you to play the games that Roku hosts.
The 1,2, & 3 all offer you an RJ-45 port so that you can run a physical line to the box. Also those models give you an infrared control, so you can utilize a universal remote.