In the process of prototype building, one of the major problems that you encounter is stair-stepping. Since you will be used a layered approach for manufacturing even the most complex of the custom-designed parts stair-stepping will be an inevitable result especially with the thicker layers. The layers always have thickness that is finite. However the layers that are thinner in comparison always have less stair-stepping problems. Even in such cases the affect is visible.

One of the rapid prototyping methods that can overcome this problem is the Inkjet systems. They produce the thinnest of the layers. The advantage of using the inkjet systems is that each of the layers is milled flat after deposit. You can have even a layer with only 0.0005 inches as thickness of the layer concerned. Of course the thin layers may slow up the building process a little. But the stair-stepping will no more be as prominent as in case of thicker layers.

It is true the variable layer thicknesses could speed things up quite a bit. You can also speed up things using the jetted photopolymer based methods. They could bring up layers up to the thinness of 0.0006 inches, fractionally higher than the inkjet systems. You can also use Stereo-lithography for the purpose. However the speed will not improve visibly with the change.

What you really require in such cases to bring up rapid prototyping with high speed is an experienced player in the field. ZoomRP.com is the fastest rapid prototype service available and most your problems will be resolved when you obtain their services.