I'd chose maya, because thats what i use (thought i also use MAx) Renderman isn't a 3d modeling program, it's a renderer that can be used in maya (instead of Maya's MEtal ray renderer)
Only problem is Maya is expensive and so is max, XSI is very cheap but good, but if you want free i'd go with Blender. If you want to get into game modeling in animation you can do what i do (use Maya for modeling and Motionbuilder for animation). Most 3d engines (like Kaneva game platform which i am useign for a mmorpg) perfer eather Max or MAya, and Max is far more widely accepted as a game modelers tool of choice, but i personaly like maya.
SO in short...
MAya: Best tool by far in my opinion widely accepted in the game industry and has been proven agian and agian in the movie industry.
3d studio Max: Perfered artest tool by most game engines. I dont know much about this tool. Has some pretty neat features, and many plugins and inhancments
XSI: Around $500 realtivly suported in many game engines.
Blender: Free, good tool. Constantly growing
Renderman: Rendering Tool that can be used in conjustion with maya (look at starwars ep III)
Deside which works best for you. MAny of these tools have free aditions, Maya has a Personal learnign adition you can download and use for free, no plugin suport though