Until today I had an XS Big Dot Trijicon up front and the stock M&P rear sight (I did not like the shallow V XS rear sight). I have tried to get used to the Big Dot, but finally gave up and installed the XS Small Dot today. The problem I had with the Big Dot, is it shot low unless I completely covered the bullseye with the front sight or even higher. I prefer a 6 o'clock or a little higher hold. I imagine the XS Small Dot will be a little more to my liking. Call XS, they have many night sights available not listed on their website.
I had 3 dot night sights on my Kahr, but the rear sights were very confusing at night - my eyes suck at night. I replaced the rear night sight with a standard site, and it is now much easier to pick up the all important front sight at night.