I think that is why my 2 MOA Holosun looks the same size as my 6.5 RMR. But the RMR is more round with less flare, probably due to not having to crank it up so much.
What I've found to be more important than size is intensity of the color, and the shape of the glass. My burris dot isn't very bright-not like it's turned down, more like the red is dull. Also, I like the wider shape of the sig romeo or the venom. As for dot, bigger is faster but I haven't found dot size to be the number one criteria in which dot I like best. I also like shake awake feature, and suppressor height sights as backup just in case the dot doesn't work.