how durable are sig's coatings when compared to tenifer, melonite, H&K's h.e coating etc...? are they higher maintenace? it seems nitron is the main coating but are there others? are there coatings i should shy away from that they have? i know nothing about sig's, just considering adding one to the mix to compete for my purchase against an hk45, as i recently took the fnp45 off the list. and no 1911's! the two im considering are the p220 elite and sas full size.