I'm talking subtleties here.First,I have an M+P c,not a Shield.Similar.
I'm not used to three dot sights so much.They do work,and I think the original sights are good.My old eyes,the rear sight dots dominate a bit.I have to work a bit on "turning up the volume" on the front sight.Or turning the volume down on the rear dots. A -o- in white might be good.
On my 1911's,I prefer the 10-8 rear U-notch,fixed semi-original type sight ..just steel,and a Trijicon front night sight.
I'll concede a fiber optic front might be better.Despite my thought that trouble often occurs in darkness,I weigh that against positive ID of the target.
Unless the target is muzzle flash,I need enough light to know I'm not whacking a friend or relative.That may be enough for fiber optic.Have little experience with them.
I,myself,might try U-notch and fiber optic,ot Tritium Fiber optic front only.
At 7 yds or so,the XS big dot might be fast,and plenty..but I'm not so sure about a 15 yd CNS shot.Some degree of precision is a good option.I can't say I have experience with the XS.I am assuming.
For myself,I can't say the factory sights are deficient.