I recently added Big Dots to my M&P Shield. I was skeptical at first but after I tried them, I really liked them. I've alway had a hard time picking up the front sight – alway focusing on the rear sight. These sights allow me to pick up the front "big dot" very easily and while improving accuracy. You'll find everyone has a different opinion on sights.
Depends what you are looking for. I wanted night sights and went with hackthorn sights from ameriglo . I have xs big dots on my glock and I like them as well. I went with the ameriglo to try a blacked out rear with a lighted front sight.
If you want night sights I can suggest Glow-On luminous paint until you can find a good deal on some good ones like Trijicon. I have those on my full size M&P40 & they're good but will probably need replacing soon.
I didn't think I'd like the factory sights on my M&Ps after coming from Glock pistols but after about a half dozen rounds through my FS & compact I deciding they were good. Now with Glow-On & the factory supplied Trijicons (the gun was bought used from Police service) I have very usable sights in the dark.
The sights are really great--the fiber optics catch the ambient light during the day and light up great with a distinctive white ring around the front sight--can't miss it day or night. But at night, they light up out of the safe--no matter how long in total darkness--unlike glow-in-the-dark paint, which needs a recharge.