What I guess is new as compared with mr02 just by looking at this picture:
1. shorter chassis that allows 90mm wheel base but keeping MR & narrow (zero) offset so it fits nearly all body shells
2. less space for pcb and thus only 2.4 Ghz or even newer pcb can be used (no more room for ad band or am pcb)
3. newly designed servo (smaller to allow space for the batt to move further to the front.)
that's what i thought at the beginning too, but after thinking carefully, the distance between the three body mounting points are fixed, so shortening the chasis wouldn't help. (at least for existing bodies)
but i agree with no.2 & 3, and that there's no great improvement