I used to always have rubber mats, keeping the original carpet mats in perfect condition... for the next owner. Now my preference is to use the carpet mats. They seem to trap the dirt, unlike the rubber ones, which when dry, tends to roll about and get on the carpet underneath. Or when you get in with wet shoes, you end up with a puddle on the rubber mat, whereas the carpet mat soaks it up.
Regular brushing and vacing keeps them looking good, but as they do start to age, they are not that expensive to replace.
