Levels made from blocks render very slowly. It's hard enough getting a block-only level to render even a half million polygons per second on a good card. A model-only level renders at least 80 times faster, allows for freedom of shapes and sizes, and otherwise much more flexibility. The only two weaknesses are lighting (which can be a little tricky to get right since static lights don't affect models, dynamic lights do) and collision (which is a bit tricky to get working right, but once figured out, it's no big deal). From my benchmark tester program (on the downloads page), Gamestudio in a model-only level, is capable of rendering over 350,000 polygons on today's midrange video cards at 60 fps. A block-only level couldn't manage 1 fps with this many polygons in view. This scene, on my current setup, renders well past 200 fps and it doesn't use collision, LOD, it's not optimized, and there's something like 60,000 visible polygons. It's a model-only level I haven't done much with since September 2005.