Fieldguard are the best IMO .. not the cheapest. I have mats that are over 20 years old which show absolutely no sign of wear. Easy to clean and to lift for the mega spring clean too.
Another vote for Fieldguard. Mine are also over 20 years old and are as new. I even have some laid on uneven bare earth (not recommended by the manufacturers) in a field shelter and they are brilliant. Well worth the extra initial outlay.