There is no “best” as each type has its benefits and liabilities. There are three types: sand, cartridge and diatomaceous earth (D.E.). All will do a fine job with keeping a pool clean. DE filters will remove debris down to the smallest micron, then cartridge, then sand. And one can add filter aids to assists in getting out the smaller debris. The most environmentally friendly one is cartridge as sand and DE use chemically treated and maybe heated pool water in the process of cleaning the filter (called backwash). Cleaning a DE or sand filter is quicker than with cartridge but it is the wasted pool water that is the main issue. DE filters have the dirty DE powder that must be addressed (a separation tank may be utilized or one will have dirty DE powder in the backwash area) and the sand in a sand filter must be replaced periodically (every 3 to 5 years) and is not something many homeowners are ready to do themselves. Aqua Pool uses mostly cartridge filters as they tend to filter better than sand, almost as good as DE, and do not have the issues of handling the dirty DE or wasting of pool water.