XS Sights on pistols are a gimmic. For defensive shooting you can shoot just as fast using point shooting, slide index, front sight index, or soft sight picture relative to the distance to the target AND if you have real sights still shoot accurately at range or at smaller targets. In my AZ Armed guard classes people with XS sights generally get lower qual scores or fail to qualify on a full size human target that isn't moving. Hand them a Glock with trijicons or even crappy factory plastic sights and they do better,
They are unsuitable for match shooting. Over the past several years I've seen a half dozen shooters show up with XS sights that they insisted were awesome for self defense, fail to be able to hit static steel roughly the same size as a human head or spend a lot of rounds doing it. Give them traditional sights and they always perform better. It is a complete fallacy to think that equipment that makes it harder to shoot well under static match conditions with much less stress will suddenly perform better under more stress with rounds going both ways.
The XS sights on shotguns work great.
I use the same iron sights for competition that I carry, Warren tactical Sevigny carry sights.