Note that the axis is built on the E450 chassis (albeit the bare chassis rather than the cutaway version), so doesn't have as much of a difference there as you might at first expect. That's not to say your observations of foot room, space, etc. are incorrect; however, it's also quite possible that there are some class C motorhomes with mostly similar features in those areas.
All, or practically all, other gas class A's are built on the F53 motorhome chassis, which has a few more differences. I think even with the new engine the F53 gets a higher power tune/setup; I know for sure it was a more powerful version with the V10. There are other chassis differences as well.