I've used Vue since version 4 and I've always found it to be reasonably stable, but - and it's a big but - I have never used xStream. By all accounts I've seen, this is one of the buggiest, least stable apps which are sold for pro use on the market. I can tolerate the occasional Vue crash since I don't do this for a living. I suspect that if you do CG work professionally, your whole attitude towards reliability is very different!

I'm also a C4D user and I can confirm that Cinema is a very user-friendly and easy to learn interface; Vue's is okay but it's not as good as C4D, IMO. This is in part due to its non-standard approach - not as off the wall as Poser or ZBrush, but different enough to make things... interesting.

Steve