Depending of what you want make
Hobby or work
Illustration sculpture animation manufacture...
Rhino is fine for all mechanical design production! (and Michael is one father of it ;)
Amapi mixes nurbs and polys but no so easy to use (exotic UI )
the more easy free one is Google Sketchup (if you want not modeling "monsters" with millions polys for ultimate details)
and for all that you will need renderers for presentation of images: a free one Kerkythea because it accepts the Ngons of Moi! ;)
If you have money don't hesitate Rhino will be very strong and you can add a polymodeler like Silo Hexagon...Amapi ;)