Vue 6 should have the best compatibility when it's finally out. All other solutions need manual adjustments and by that fail the easy part in my opinion. It's really hard to give you any advice as long as you don't say what you intend to render. If you're doing close ups mostly and rely heavily on displacement maps, then Vue 5 and Carrara 5.1 are not for you (Vue 5 can't do displacement maps at all, Carrara can only do one map per object - so that's no good for objects with more than one map - so about all current human figures...). Oh, and Bryce 6 fails the fast part...