The 8MOA (or even 6) is the one I use for acquiring the threat
fast. At a hundred yards it'd likely cover most of a threat's "mass".
But then who is using a pistol at that distance? Or fifty yards?

For precise shooting___like target shooting paper or for 6"
steel gongs at thirty-five yards you might prefer the 3MOA.
Although I've used my 8MOA for 6" steel gong targets.

Its my belief and understanding the size appears larger the
brighter it's set.
I'm familiar with the Burris FF3 and Sig's Romeo 1.that's set at
3 MOA.
My very most favorite sight is the Shield RMS. (Made in UK) I chose the 8 MOA. (For SD ) It's small. Its on constantly with no
buttons at all. The brightness (Big in bright daylight) adjusts automatically instantly to the environment.
The battery lasts 2-3 years. Sells most places for $400. Lone Wolf
sells them for $349. (If you buy from Mfg.in UK> $400 + shipping.
So, it depends on how you intend to use your reflex sight.
Hope this helps.
Stay safe
Poli Viejo