I think Amapi Pro is a more of an all round modeller then Modo. Modo is part of the SDS Nendo/Mirai winged edge craze that is going on at the moment. I don't think Modo does Nurbs at all. I think Modo was created to fill the gap that was left in the Market when Mirai disappeared. That being a VERY powerful but easy to use modelling, texturing and animating tool with a nonlinear work flow. Since Mirai many apps have emulated its feature set (Wings, Silo and some of the big name apps have borrowed ideas). One interesting application that is on the way is Madsie Freestyle. No real demos are avaliable at the moment but the developer seems to be on a similar path to Modo albeit he wants to release a freeware version and also make a pay version that is not too expensive.