I would imagine that the disadvantage of the 3100 / 4000, will be a lack of sampling, and audio recording. All other features would be the same.

Lightweight is a big plus for me as I travel very often and end up paying $210 for a return trip in overweight and oversize. If the key feel and the pitch and modulation wheels are a little more substantial on the successor to the 3000, I would probably get one - just for travel!

Chony