I have Force on one bike and Red on another. The main difference to me is the amount of throw to shift from the little ring to the big ring. In particular, I have trouble with Force when its cold and I lose feeling in my fingers (I have
Raynauds)
So, is the throw easier (more Shimano-like) with the Red Gruppo on upshifts from the small -> big ring? That's really my only little niggle with Force and Rival. I have them on the two bikes below. My wife has 105 on hers, and I had forgotten how easy an upshift was on that set.