Cars will roll freely when they have an almost 1:1 internal ratio. The more internal front drive you have, the more drivetrain drag you have. The MTX3 has that drag feeling when the 16/19 belt conversion is being used, but when the stock setup is being used, it's pretty free. The 16/19 setup feels almost like a soft drag brake to me. I use it to drive on power deeper before a turn. I've only driven the 710 once for about 20 minutes and found the lack or steering intollerable for me. But being able to access the diff so easily makes the 710 pretty sweet. My times were definitely faster with the Mugen. Just my two cents.
If anyone's interested in understanding internal ratios better, go to
www.sgrid.com and find the Art Carbonell Forum (Former World Champ and current Serpent USA Team Driver/Setup Guru) and he's got a great write up on drive ratios and how they affect your car. Really made me understand it better