Pool Builders ALL give the same line on cartridge filters. We hear this from all over the country and I've heard it in my own neck of the woods far too often.

You will find that almost ALL home-owners HATE cartridge filters--very few can figure out how to make them work well. It's possible, some do, but most find cleaning them to be messy, unpleasant and very time-consuming.

I suspect there are 3 self-serving reasons builders push them:
1) the plumbing is easier--they don't need to plumb in a backwash/waste line on a cartridge filter. Carts are simple to use and understand (just a terrible pain to clean--replacement cartridges are far too expensive for "throw-away"--you have to clean them.
2) There's no six-way valve--better margin for the builder.
3) The first season, you usually don't have to maintain the cartridge at all, until the season's over. By the second season, when you discover you HATE the thing, the warranty and his obligation have expired.

But ALL the pool builders push cartridges and SWEAR by them. I'm guessing that there must be something their association pushes. Homeowners here will give you a VERY different take.

I would much rather see you go with a DE or Sand filter. DEs filter the best, but we have some inexpensive tricks here that get a sand filter doing nearly as well. A cartridge DOES filter finer than a sand filter (not a DE though) but if you use our FAVORITE sand trick on the cart, you'll ruin it.

Many people run sand filters without our tricks very, very happily. Sand is easy--if you take care of it, you rarely, if ever, have to change it. DE is a little more labor intensive, but those who use them get into the routine and have no trouble.

Whichever you go with you want the builder to put in a waste/backwash line. This allows you to pump down the pool's water level using the pump, rather than a syphon or submersible. Furthermore, if you get an algae bloom down the road, we always recommend vacuuming every day TO WASTE. Can't do it if there's not a waste-line--and there probably won't be with a cartridge filter.

Notice that if you decide to change to DE or Sand you'll now need a waste-line--and it's MUCH cheaper to install at the beginning than later.

Besides, didn't make you suspicious when the builder told you it was a DISADVANTAGE that a DE filter filtered out smaller particles than a cartridge? Most of us, here, PREFER better filtering to worse filtering!