If money allows, get the bigger pump, you can always put a ball valve inline to regulate the flow. Or, like what I did with one and in process of doing with the other, run a "T" off the return line to a ball valve and then you have an additional source for some flow if needed. Mine goes to a little rubber maid plastic box with mangroves, then a gravity feed back to the sump. This is of course if you are using PVC.