Originally Posted by Ragnarok

Generally speaking, the Executive Aisle have a good variety of cars including full size cars, compact and mid-size SUVs and occasionally higher end vehicles. This forum has threads on many of National locations (esp. major airports) with Flyertalkers reporting back the vehicles available in EA/ES. Here's EWR for example : Cars at EWR - Page 26 - FlyerTalk Forums

There are certain locations and situations that I would recommend reserving the exact class of vehicle you need. e.g., Denver during peak ski season and you need an AWD SUV. In those cases, my understanding is the after booking the specific class of invoice will reflect that you are charged at one-class lower rate.

You can go ahead and make a dummy reservation for a future date to test it out, there is no cancellation fee for a non-prepaid reservation. Just cancel it fast so that you are not messing up availability for others.

Originally Posted by AutoSlash

Cars in the aisle are usually at least fullsize so it doesn't really matter whether you book midsize or fullsize. You'll be choosing from the same pool of vehicles either way, so just choose whatever is cheaper.

As far as selection goes, you'll often see SUVs in the aisle, but it really depends on how you hit it. With Emerald Executive status, you'll have a better/wider selection than the average customer, and generally, we've found that as an EE customer, if you don't find anything in the aisle that suits your needs, you can ask and they often will accommodate you, but YMMW.

Note that if you book premium, luxury, SUV, etc. then that's known as Emerald Reserve service and you choose from a different section at aisle locations.