Here below are the ONLY 2 differences between MTV3500 & MTV5000:-
1. MTV5000 has control button on the set-top box. If you cannot find the remote, you can use the buttons on the set-top box while MTV3500 totally counts on the remote.
2. MTV5000's HDMI specification is 1.3 (latest HDMI specification) but MTV3500 is HDMI 1.1. So, if you have a TV with HD ready only, MTV3500 probably is okay....if you have latest TV with full HD, MTV5000 will give you better quality.