Do you think there is really that much of a difference for CCW to give up the two rounds? Looks like around .7" longer in the grip w/o extension of the 45C. With the extension probably .25" difference. Barrel is the same at 4".
I went with the Mid Size 45acp S&W, I like the grip size better, carries easily (use several of the same holsters my full size 9mm M&P uses), 10+1 rounds of 45acp is always comforting as well.