Aimpoint's the best (@ over $350) and the BSA is the worst (@ > $40).
As for which is better between the holo & the dot, that's a personal preference issue. (Also, bushnell bought out eotech and they have the same product for about $100 cheaper while pretty much the same thing. Might want to also check out bushnell's red dot, I heard it was reasonable for the money.)
nssa4914 no offense when I say this but putting a aimpoint on a shotgun is like using a scope for carpet bombing. I think I would try ghost rings first IMO( hope no offense is taken)
TNT, I have Ghost rings on my Benelli M2 right now and found out the hard way that they don't work in low light
PS My benelli can drill golf balls at 100 yards with Lightfield Sabot's
C-more, Gilmore, OKO, Aimpoint, and probably a couple others. You get what you pay for in a dot sight just as you do in a rifle scope, there is no comparison between the cheap units and the costly units.