I got a Sig P320 M18, simply because the Marine Corps adopted it as their new service weapon.
Its my least favorite pistol, not saying I dislike it, more I enjoy all my other pistols more. I enjoy my XD-M's more than the Sig. When a bought some magtech 9mm ammo in bulk, I was getting a few duds, I had several rounds that did not fire in the sig, soft strike on the primer, that I loaded in the XD and they fired.
My brother is a Sig fan. I have to admit his P320 X-Legion is the smoothest most balanced 9mm I've ever shot. His P220 is very nice as well.
I looked at a P220 in .45ACP, but ultimately it was a single stack magazine, so I went with the FN FNX-45 Tactical. I have good impression of Sig, although a little cautious about the P320 (remember the M18 has a manual safety, that was the assurance I needed to get it). Sorta like Glock, every time I consider one, something else catches my eye and draws me away.
My son is a Glock Fan, that likes Sigs, but has discovered CZ and has suddenly become a CZ Fanatic on his way toward his 2nd CZ. He has CZ-97 and looking at the P10 now. If you ever shot a CZ, they are nice pistols.