Illustrator is Vector based, photoshop pixel based

Which means you need to ask yourself where you will use it for, I personally don't like illustrator but since it's vectorbased it's better scale able than PS.

The same goes for Poly's vs Nurbs, poly's are pixelbased if you want a highress render you" ll have to up thepolycount to keep the curvature consistent at higher resolutions, nurbs define a curve between a number of points and it retains its shape at higher resolutions.