It all depends on what kind of circulation you want, what kind of fish, do they like fast water or calm, how much you are willing to spend...
The prop style powerheads are the most efficient and quiet, but all they do is circulate water. The pump style can be used to introduce air into the discharge aerating the tank....not so quiet...but generally cheaper..
The prop style magnetic drive powerheads operate outside the tank with only the propeler inside the tank...no heat transfer and usually very ADJUSTABLE flow wise...super quiet...very expensive.
Without more info, a targeted solution can't be made.