Well the way I look at is this, flow pumps are great for closed loop where there is little head pressure to overcome. The impeller design is as such that it is a free flowing design that does not take a lot of power to turn. A pressure pump is a whole different story, they are good for things like high power beckett skimmers and basement return pumps. Their impeller design is much tighter tolerance and more restrictive, and hence requires a lot more power to run the same type of gph at 0ft of head. But you put 15ft of head on both pumps and the flow pump will be basically shut down because of its free design, the impeller will basically be treading water inside the head unit. A pressure pump will show very little difference. A lot of pressure pumps can pump water up to over 30 to 40 ft before they get shut down. So basically what i am getting at is that it takes about 1 amp to run a 3000gph ampmaster and it has about 3200gph at 0 head. When you switch over to say a pressure rated sequence it is more like 4 to 6 amps to run 3200 gph at 0 head but it will still be running about 2500 gph at 15 ft of head, but boy does that sure add up quick on the old electric bill. I hope that made sense and mind you I am not quoting anything from spec sheets, that is off the top of my head, but it should give you a idea of what to look for in your application when looking at pump curves and power drawn.