I've got a P226 in 9mm and several 15 round mags. Now, the P228 holds "only" 12 or 13.....
I've also got the P226 in .357 Sig. I agree that if you want one gun for everything, get the P229. It's a lot easier to carry than the P226 and it's just as accurate. That said, the P226 is great. Accurate as hell, reliable, and it's got the best DA trigger I've come across (in an auto). I'd get the .357, then add a 40 barrel and a 9mm barrel and 9mm magazines after.