I have done renders with F4 and the Genesis male together and I can't see any difference in the quality of models in the fully rendered image.  I think what will make the Genesis figure look good or not are the same factors that make any other 3D models look good or bad--the lighting and the texture map used on the figure. 

I don't think Genesis is any more expensive than some of the other 3D figures and clothes I've bought--but the big advantage is that any clothing, texture or hair bought for the Genesis figure can be used with any variation in it's shape.  The more shapes you  have to work with the more unique characters you can create.  You never got that kind of versatily out aof clothing, hair, or a figure before.  No more converting outfits from one figure to another.  The workflow is easier than the series of morph injections one has to use with M4 and V4.