SIG P220s have a reputation for being the most accurate DA/SA .45ACP pistol out of the box.
If you are going to get SAO, you may be better off with a 1911. Proper SAO carry is Condition one. Hammer back, safety on. The small safety control on the P220 may be slower for some folks to operate under stress than the 1911.
On the other hand, if you are transitioning from 1911 to SIG, you may prefer SAO for the familiarity.