To me, they are all the same... they just recirculate water. The regulator is more important, IMO.
Most people just recommend what they have (not all), but I have used about 8-10 different kinds and each of them has some strong points and some weak ones. Ehiem pumps are nice because they don't get loud or break down when small pieces of media get into them - they also last a decade or more. I like reverse flow, but this is not as big of a deal with larger media now available.
Just get a brand that you have heard of and can trust. Used is a good way to go. I have used and like MR2, MRC, Knopp, Korallin, Geo, Octopus (not my favorite), AquaMaxx, LifeReef and a few others that I cannot remember.