My Volvo V50 had a carbon filetr in as original spec, I mad ethe mistake of throwing a cheap one in there at one service and it was noticably poorer, lots more odours getting in, hayfever off the scale etc. I switched back to a carbon filter and it was all well again. I’d say most cars are pretty good, obviously you get better ventilation controls the more expensive you go, mine’s got auto climate which does a very good job of keeping temperature stable. I’m not sure if one cars ventilation is better than another though when you compare manufacturers…