Mike, I was as curious as you and took the plunge. sweet pump. I love my mp20 so much Im getting a pair of mp40s when my new tank comes in.
the flow is so wide it affects the water column in both directions. youve probably heard people refer to the "undertow". this is where the vortech beat out other pumps. Ive had maxi mods and used tunze which have nice strong flow but more concentrated, like a fire hose, and consequently dont have affect as much of the water column as the mps.
with the vortech you can see the water being being pulled back like a tide. its funny when you see fish trying to swim away as they get pulled back towards the pump. so fish get a larger area to swim against 2 different currents.
if you want to save some dough, let me know, Ill be selling my 2 month old mp20 when I get my 40s. I have to because "you know who" told me to in order to pay for the new guys!