and most importantly, animation.
A:M can import common polygonal formats (that's what you are talking about) but these models are rarely suitable to conversion to splines, which is what A:M uses. Most models will need to be substantially reworked if you intend to rig and animate them.
A:M is introducing ambient occlusion in V13. V13 is still in "alpha" now, but A:M owners can download and use it.
I think the math of 3D rendering is pretty well established now. I doubt that any of the apps has a secret that dramatically increases their speed, all things being equal. If you want faster these days, you need faster hardware.
Yes. A:M is a unified environment to model, rig and animate without need of other programs.