Honestly, consider a PC for 3d.
Apple just has not cultivated the 3d market very well. OpenGL and video cards both seriously lag.
My money is where my mouth is, I'm heading towards doing my 3d on PC and my main 3d app (Cinema 4d XL) is a great Mac product.
What will happen is, you will be able to do most any and all smallish projects. But you may have issues with larger more complex models and scenes. Poof, dead-end.
Consider the Dell Precision Workstation laptops. They come will decent quality OpenGL cards.