We rented from the Double Tree last time but when we dropped it off there was no one to take us back to AKV an hour wait so we took a taxi. $20. But when we wanted to be picked up it was just a few minutes and from drop off till engine start was 10 min.
The MK rental site is the easiest. However, the closest is as the Swan and Dolphin resorts. I would check both out online to determine if there are any advantages at either location. If not, the distance between the two from AKL is negligible.
There are several agencies in the hotels at DTD. You could take the Disney Bus to DTD and just walk to the hotels (5-10 minutes). You could also take the bus to Disney Studios and walk to Swan & Dolphin. (5-10 minutes).
Alamo is the easiest. They will pick you up at the hotel.
There are lots on the main road below AKV (if you take a right coming out at the entrance it is about a mile down), the care rental agencies are about a mile west. All the "offsite" rental places will pick you up and drop you off at no charge. I used Hertz.
THey are signifanclty cheaper and have no "concession fees"