Tell me about the RB67 and its lenses

My RB67 is heavy. I have the 90mm it and a prism finder. Very heavy. I shoot a Hassleblad now but still own my RB67. I like the Mamiya's close focus ability much closer than the Hasselblad. I like the Hasselblad lenses better I have two a 50mm and a 150mm. They are better sharper etc.