I like the cartridge style, as well. I think Pentair and Hayward are pretty equal. Our pool is @17K(?) and with the 4 element Pentair I clean it twice a year, and it still doesn't register restriction on the gauge.
The newest ATCs are nicer inside. Vinyl/composite flooring, and the cabinets, while still aluminum, have a much more residential look, and new pulls/handles. My wife was not digging the previous race trailer look at all LOL