So I have a 9mm P320C that I really like and have a line on one of the 45 compact models. Always liked the SP2022s though and shoot mostly 9mm anyways. If I went that route, it simplifies my ammo logistics in that I only have to track and buy one caliber. The flip side is that this would be my only 45, it'd work with all the P320 holsters / parts I currently have, can act as a backup for the 9mm if something fails, and would probably be carried a little more than the SP2022 would. What's the consensus on here?

I have a SP2022. It's my gun I keep in the car. They're reliable and shoot great. Honestly, they're more Sig-like than the P320 is.

I would get a second Sig P320 a FS or a SC or another Compact.  

That is what I would do.  I need 2-3 of each gun I run.

3 Glock 19s
2 Glock 17s
3 Beretta 92s
3 HK P2000s
2 HK VP9 (looking at getting another)
1 Glock 26 (looking at getting another....or do I want a VP9sk.....I mean two VP9sk......
It is just fun to have more than one.

I was thinking down the road when the M18 models come out I'd grab one of those. But in 9mm.