Honest answer: depends on the agency, depends on the vehicle. I started renting recreationally as soon as I turned 25, almost exclusively with National due to their "Emerald Aisle" followed by access to the "Executive Aisle" gained through my Amex.
When it came to the cars from National, I treated them with the utmost respect. One of National's selling points was their focus on maintaining a young, diverse, low-mileage fleet and it showed. Even the basic options presented well: no 50k mile Versa's at the National lot that's for sure.
My single best experience with National occurred while visiting family in Spokane. Small airport, smaller rental inventory. As an Emerald Club executive member, I quickly found that most counter agents were more than happy to give me a vehicle WELL outside my midsize reservation.
For those unfamiliar: As an Executive member, making a reservation for at least a midsize car grants access to a dedicated "Executive Aisle" of choices guaranteed to be at least one tier above a midsize. Not all airports provide aisle service, in which case said executive member is guaranteed at least a 2 class upgrade.
GEG happens to be one of those airports. Before I ever approached the counter, I walked out to the lot and surveyed my options. After rows of Buicks and Jeeps, I spotted her: a brand new Infiniti QX56. Pearl white over black, sitting wayyyyy back away from every other car.
I walked in and up to the counter, did the usual yada yada, during which the agent revealed the bore-fest I'd been assigned. Fully expecting to be rebuffed, I mentioned the QX I'd seen and asked about an upgrade (with full intent on an upcharge). Long story short, I was handed the keys to a fresh off the truck, plastic still on the interior, 175 mile beast of a weekend ride for NO CHARGE. I think I washed that thing 3 times in the 5 days I had it.