I carry off and on for 43 years, the last 10-14 it's been a 26 or a 27, and now a shield in 40, since I carry 2 guns most times, I sometimes mix it up, also with a 30 and an xds, they are all great, the 26 conceals the best with a 10 rounder in it, and is the lightest. After that it's just a matter of taste, I like a 9 or 40 for my backup, and a 45 for my primary, The xds suits me fine for that, with 2 extended round holsters it is terrific.
You need to decide that you are going to carry all the guns you carry with a round in the chamber, so holster choice is most important with glocks.
The shield has a safety and the xds also has a grip safety, for me I prefer the gun in my groin to have a safety of some sort on it.
also I prefer a wider grip, so gocks work for me better as far as stock, the others need a hogue or other grip modification or they get too thin for my large hands.