There are a lot of things to consider. Do you have any features that require the pump to be on high speed to operate properly? Automatic cleaner or In-floor cleaning? If not, can you get the circulation you want without running on high speed at all? Maybe you only need to run on high speed when you want to quickly skim some debris from the surface?

I have a 2 speed pump, and my pool builder sucessfully sold me on the benefits of 24 hour-a-day circulation. Public pools are required by law to have 24 hour circulation. I run on high speed a few hours in the AM when I am likely to be adding acid. A few hours in the middle of the day to increase the flow through my redneck solar in the peak of the day, and a few hours in the afternoon when we're most likely to be in the pool and might want to turn on the fountain or sheer descent. The rest the time I run in low speed. My water is continuously filtered and sanitized by the SWG which I run at a much lower percetage. I know my circulation is overkill, but it only costs me a few extra $$ a month and my pool always looks great