Thank you for all the comments.
I'm not so interested in the Mamiya RF system. I was but then I realized that I prefer 35mm (3:2) normal and wider lenses and 6x6 (1:1) for normal and longer lenses. I know that I can crop and such but too many systems is too much money! I've pretty much settled on 35mm rf, 35mm slr, and 6x6 tlr for now. I find those the most useful, perhaps more systems in the future but I want to build my 35mm kits right now.
Yeah I've read that the 28mm f3.5 is sharper than the 28mm f2.8. I don't really care to research too much on which is sharper and the difference in speed to me, is not that much. I use my Rollei 2.8E and my Rollei 3.5E at f/4 and f/5.6 mostly. Anyways I intend on using my 28mm f3.5 and 21mm f3.5 simply to learn the focal lengths, and then take it from there.
Judging from the comments I guess there is good use for SLR and RF wide angles. This is kind of why I have both systems: one compliments the other. I'd prefer to choose one system but I don't want to live with the limitations of RFs nor do I want to live with the limitations of SLRs.