If one regularly rents from National locations with the long-established choose-your-car Emerald Aisle service, National can be pretty good. (Some big airports don't have EA service; check the list.) Use the variety offered; self-downgrade into other selections if you see a more appealing vehicle. Quick. Easy.

Locations that lack Emerald Aisle mean having a car assigned: this is usually described as Emerald Club Counter. I'm willing to walk the lot and ask for something specifically and often agents will play along (consistent with the car class reserved.)

Lots of places - off-airport, small airports - lack National locations and one will be pushed to Enterprise. The service experience is entirely different. Rather than quick 'keys and go' from info in the Emerald Club profile, one is more likely to encounter firm, repetitive efforts on insurance, fuel, and car upgrades.

No matter what, one needs to know the rules: to maximize benefits under Emerald Aisle rules, and to protect oneself from BS with Enterprise. If knowing the rules, and expecting the rules to apply to him even if renting 225 days a year, are beyond the OP, he is unlikely to be any happier at National.