I haven't looked into what WP I should get yet. But as an E36 guy I'm surprised you like Graf. They get a pretty bad rap and are at the bottom of the metal impeller brands.

I know composite wasn't looked at fondly because early versions would get brittle and break apart but the new ones are better. I put composite in my E36 a couple years ago, and if composite is standard on these, I'll do the same.