Why use a Disc Filter? Disc filters excel at stopping organic material, stuff that would clog up a screen filter very quick. The downside to a Disc filter is that they take longer to clean. You must take the filter apart (not hard) and take the discs out of the holder and rinse them under clean water. It can take a good ten minutes to do the entire process. You cannot flush disc filters by using a ball valve on the bottom of the filter either.
Why use a Screen Filter? Screen Filters are very easy and quick to clean, in fact you can even use a ball valve on the bottom of the canister to do a fast flush. For sand, grit and larger debris a screen is the best because of the easy flush ability. They are also less expensive so if you need to do a group of more than one filter in different size screen mesh its affordable.