My PD issues SIG pistols; P-220s in .45, the 226, 228,and 239 in 9MM. The dept split is about 35% .45ACP and 65% 9MM. I have been the lead full-time firearms instructor/armorer for the past 12 years. As a LEO,I carried my Colt Govt or Commander from 78-90, switched to P-220 from 90-93, and carried a P-228 from then to present. With all that in mind, here are a few of my observations:
1. The P-220 is probably the most accurate service pistol right out of the box.
2. The P-220 is much more finicky about duty ammo than any of the SIG 9MMs. Winchester RA45T work just fine.
3. I see 10 times more parts break in P-220s than any of the SIG 9MMs. The 9MMs are just much more reliable. That's the reason I have carried one as a trainer and as a SWAT officer.
4. P-220 magazines have experienced several changes. The early "small zipper seam" mags had poor top welds and were prone to splitting. We replaced all of those with the later "trapezoidal seam" mags and have not split and of those. Heavily used mags may develope small cracks from the rear feed rail cut, causing the mag lips to lose a certain amount of tension. We have not seen very many of these but they do occur and the mag should be replaced. (the SIG 8 rounders are trash, stay away) The newest stainless, made by Mec-Gar for SIG, seem to work alright but we have only been using them for about 3 years.
5. Early P-220s, without the hammer reset spring, were surplused out as a safety hazard, relating to the decocking lever vs thumb relax issue.
6. All of our SIG are surplused out after 10 years of in inventory. This is done primarily due to the constant changes made to SIG pistols by SIG and the failure of SIG to communicate these changes to their SIG certified armorers.
Overall, SIGs are pretty darn good service pistols for LE use, but the 9MMs will prove to be much more reliable and durable than the P-220 .45. I would not use a P-220 .45 in any demanding military role which required the pistol to be fired ALOT. If you are going to fire this P-220 pistol ALOT then you'll need spare roll pins, trigger bar springs, trigger bars, slide catch springs, locking pieces, trigger pivot pins, and hammer reset springs. Or, you could just carry a P-226 or P-228 in 9MM, know that your pistol will work,pay attention to shot placement, and have a wonderful life.