I'm with Phoenixrising here. . .Wings is perfectly fine, and while I've never made much with ZBrush, those who are good at it do amazing things. I'd cast a vote for Rhino, especially if Nurbs are your thing. . .its very smart and well designed, and much more robust than most Windoze programs (I work in 3D Studio a lot, because I know it and it works for me . . .but it crashes fairly regularly, while Rhino is significantly more stable)