I asked this around on other forums a few weeks ago, and mostly everyone seemed to be in favor of a maxed turmoil pure. It does cost a lot of money to get there, but I guess it's the best, if not, one of the best pures out there. I myself am working on a hybrid.
It depends on what. The best rushing pure is Dark Bow rusher for 40-50 cb and Dclaw rusher for 70-80 cb
For a normal fight, I'd say obby maul pure is best for 40-70 cb and zerker pure is best for 70-95 cb. and barrows pure is best for 104+ cb.