Natal lacks the ability for multiplayer - you can motion sense multiple people, but no way to distinguish
Natal lacks IR, which is the major navigational method on the Wii.
Natal lacks the ability for button/analog/d-pad + motion combinations.
It may track motion well, but there is not much that can be done with it. Perfect motion tracking is not necessary to make a great game that uses motion controls extensively.
I describe myself as a little dose of toxic masculinity.