I don't know about Universal or Sea World (I'm sure someone will help you out with those). At the Disney parks, most of the
AAA lots are next to (so a little bit farther than) the Handicapped parking; at WDW, they call it "Medical Parking".
If you have a wheelchair or
ecv with you, you need to park in the handicapped parking area.
The regular parking lots have trams that go from the parking area to the park entrance, but the handicapped parking areas don't. If you can step onto a tram and either don't have a wheelchair or have one that folds (and someone in your party can hoist it up onto the tram), you would actually end up walking less if you park in the regular parking lots. Let each CM that you come to know that you have mobility problems. They try to save spots at the end of rows near the trams for situations like that.
They do have a limited number of wheelchairs at the handicapped parking that can be borrowed to get up to the park entry turnstiles. You turn it in there and can rent a wheelchair or ecv in the park. Since the wheelchairs at the parking lots are up for grabs, there may not be any when you get there.
Specifically, at MK, everyone has to go to the TTC and take either a boat or a monorail across the lake to get to the park turnstiles. The regular lot tram drops you off right by the TTC; the handicapped parking is a bit of a hike. The boat that goes to MK is a little bit further walk than the monorail, but to get to the monorail boarding area, you need to go up a steep, fairly long ramp. If you are staying on-site, it's best to ride the bus since the bus station area is a short walk from the MK turnstiles.
At AK, the handicapped parking area is large and unless you get there early, you will be parking 5 or 6 (or more) rows away from the front edge of it. The closest part of the handicapped parking is at least 6 football fields away from the entrance area (maybe someone has a better estimate, but it's far enough that they have several sets of benches for resting along the way). The tram drops you off closer than the front of handicapped parking.
At Epcot, again you will be closer riding the tram. But, the handicapped parking is not bad.
