I've been a Sig fan for a long time especially the P220 which I have owned in various forms. Sig's are pretty ergonomic pistols except for the high bore axis but the M&P puts it to shame in that department. The P220 Elite is all stainless instead of having an aluminum receiver and has a beavertail. Tt also has a DA/SA trigger that I could do without as I like consistent trigger pulls at all times. But it does have a SRT trigger which has a very short and crisp reset that is nice. But I find the M&P is still more ergonomic with greater comfort at high round counts, a better trigger (once broken in, and lower recoil even compared to the much heavier all steel P20 Elite. Also carries two more rounds and the beavertail fits my hand very well whereas the P220 beavertail feels like an after though and does not curve against your hand as well as the M&P beavertail. It curves up which doesn't make much sense since Sigs don't generally have an issue with hammer bite. So the M&P .45 is cheaper, lighter, carries more rounds, and fits my hand better which makes it easier for me to shoot quickly and accurately.