Must admit I’ve not tried the 365XL. You comments on grip length make sense. The P229 is a Legion and does have a high undercut also, so that might be one reason I shoot it better (and just to be clear”better” and “well” for me is still pretty poor). I do think extra mass helps me in rapid fire, but it might just be my mental bias showing. I have small hands, so both the P229 and the EMP give me more than enough room for a full grip. I have notice that anything smaller, where my pinky is off the grip, is just too small for me. I do like the slim grip of the EMP (or any single stack), again due to my hand size. And for slow fire, believe it or not I am most accurate with my P220 Elite 10MM, which is a pretty large gun. I am a bit of a Sig fan, so it actually is surprising that I haven’t tried the 365.