I would add a 3rd type:

3. Some who's had to deal with a cartridge filter on a heavily used commercial pool.


I've seen them on multiple commercial pools, but I have NEVER seen one perform well on in that environment. As of last summer (August) Pentair/StaRite CS techs recommend against System3 cartridge filters in commercial pool applications.

I grant that the seem to do well in residential applications in arid regions, but I'm pretty sure that the swimmer 'goo' I've seen clogging them in commercial applications is going to be present in Arizona, too.