I have P4/5/6/7 I use P7 with SR1.1 for most everything now. Very stable for me and I don't have a big computer. I using an old one right now.

Also has multi rendering, better clothroom, morph brush, improved material nodes, better use of OpenGL, faster when defaults are set to a reasonable setting. Every version has been better than the last.

I only use the older versions for testing and they will not be going on my new computer when it gets here, only P7 and all the others runtimes.