30 model memory vs. 10, frame rate in the 3s is 11ms only, the 3r gives options 5.5, 11, 16.5. Must run 5.5ms for digital servos with the 3r so I don't know if you can use digital servos with the 3s cause it doesn't have the 5.5 frame rate. I'm not sure if all the other options are the same between the 2, expo, mixing, etc. I have a 3R, personally I don't need or want all the telemetry crap but that's just me. DSM vs. DSM2,,,not sure hopefuly someone will fill us in on that. I do know that a dsm2 receiver will not work with dsm radio but a dsm2 radio will work with dsm2 and older dsm recievers. All being Spektrum of course.