For whatever reason, I seem to recall this question being asked before.
In any case, we do not use a large mat. If the weather turns and you get rained on overnight (or at any other time), you now have a soggy mat sitting out on your campsite. If it gets dirty or muddy, now you have to deal with packing that soaking wet mess up and storing it somewhere in your RV. No thanks.
We make a concerted effort to stay at campsites with an improved surface and then we use a small household type of outdoor "Welcome" mat that sits at the steps and which catches whatever foot debris that we do not want to carry inside.
I see a lot of people with outdoor mats covering their site, but it's just not for us. I've seen far too many of them struggling to get a wet, soggy mess sorted out that I really don't want any part of that.