I am looking at new pool filters and I don't understand something. Something that I read made it look like the C&C cartridge filter from Pentair can take a 100 or 200sf filter cartridge. but when I look for prices I am seeing two identical pictures for the C&C with one listed as a 100 and one listed as a 200. the 200 is about $200 more money. What am I missing? Why would I pay more if it is the same thing with a different cartridge?