The front-to-back length of a .45 grip frame is limited by the size of the cartridge, even if it's slim. (Any number of single column .45's can illustrate this.) That's why Glock eventually got involved with the .45GAP, so it could be stuffed into their 9/.40 frame.
If I didn't already own an excellent CS45 (6+1), an original 4513TSW (also 6+1) and a Colt OM, I'd probably have bought a G36 by now. I came close, but my other small .45's are of similar size and capacity. The last time I started coming close to ordering a G36, though, I realized the M&P 45c isn't that much larger, overall, and I'd like to have one to complement my full-size model.
I will offer the opinion that I suspect the G36, like many of the smaller .45's, may be less tolerant of shooter and ammunition influences than larger models.