Also, water features, filter, amount of time to filter, and types of debris going into pool need to be considered.
Using a Pool Skim in my extreme environment is almost as critical as having a pump and filter.
The cememtous dust I have clogs everything up very fast. Even with a big 80 sq ft filter, I need to clean it, at the very least, every 10 days. (I'm using cellulose instead of DE. It filters finer so the filter clogs faster.) For those who don't know about DE filters, this is a monster size filter for my size pool. One of the major advantages using the VF is that it will increase the pump speed to keep the flow steady. With our searing Texas sun and heat, and attempting to keep the electric use down by using the minimum turn overs a day it is critical that the same amount of flow is kept going or an algae bloom will certainly happen. As the filter starts getting clogged the pump speeds up to keep the same amount of flow for adequate turn over(s).
Then you add in some "features". A 1 HP for my pool would not keep the Pool Skim (considered a "feature" but a necessary part of keeping my pool clean.) flow high enough while running the vac cleaner. During the higher speed, higher flow cycle, to run the vac cleaner, the Pool Skim flow doubles and removes floating stuff pretty quickly, that hasn't been caught during low flow. In fact the flow setting ability allows me to set the flow so that the Pool Skim functions just well enough during lower flow settings. I can set it precisely to what flow is needed; no more, no less. And, as stated, earlier, the pump will speed up, when filter starts clogging, to keep the exact flow needed to keep the Pool Skim operational. For me this is vital. (Now that I have the experience of using the VF pump.)
This is just one example of why I can think of no other pump I would want to use. In my case a 2 speed pump would not offer this option for me. I basically have to run a pump all the time. The reason I run 21/7 is to give the filter media three, one hour rest periods during 24 hours in hopes helping it to get less cemented to the cartridges (Quad filters use special cartridges instead of grids). Using a 2 speed pump, low speed would quickly become too little flow to run the Pool Skim as the filter starts clogging.
For those who have pressure side cleaners thinking "well that doesn't apply to me as far as a cleaner". All I can say is after using pressure cleaner for 23 years, with booster pump, having to run them minimum 10 hours a day, year round, I've switched to suction cleaner that doesn't stir up the dust on bottom, gets the pool as clean in 2-4 hours as 10-20 hours for a pressure cleaner, and saves me a whole bunch of electric cost not running the booster pump for so many hours a day.
You never know when your "needs" will change. I certainly never thought I would switch from pressure cleaner to suction.
Another thing. Until a week ago my pool was doing fine set for 1 turn over a day. As the heat and sun are increasing I've bumped that up to 1.5 turn overs a day, with about a .25 turnover during vac cleaner use. I can't do that with a single speed pump or even a 2 speed pump.
Just my 4 cents.
gg=alice
