BWI is definitely a mixed bag. My company car is only a 2-seater, so I rent here a lot if I have visitors from other offices. Even exec is terrible a lot of the time. I've had the best luck on Saturday night or mid-week. I've been able to score a Cherokee and Magnum on those days, which is about the best you're gonna do.
One time on a Monday morning, they had absolutely nothing except for maybe one or two well-worn Malibus. I was able to talk my way into a brand new Cadillac DTS with 5 miles on the odometer. That was a nice change of pace, but I had to prove to the boss it was a free upgrade!