Attached Link: http://bryceblog.bryce-alive.org/

To be perfectly honest it depends on your preference

but if you have it on Mac only have it if you have either Leopard, Snow Leopard or Mavericks as it is incompatible with Lion and Mountain Lion. It is said Bryce needs a computer with at least 2 gigabyte of Ram(which is the processor speed I would say 4 Gigabytes would be great depending how you use Bryce) so it doesn't need to be as powerful as some of the other modelling programs. Personally if I have it on Windows I would go for XP because it is the most popular with a lot of people. As for Graphics card I have heard NVidia is pretty good here is a link to a site they may answer you questions better than I can. Good Luck and keep Brycing

Karl