Our last two trips we started at AK. There was no real reason, it's just the way it worked out.
We were there a couple weeks ago and we got in late on a Wednesday. So we slept in, hung out at the hotel, and then went to AK around 2 on the Thursday. We only had three hours there, but it was dead so we got a lot done. We finished with dinner at the Rainforest Cafe at park closing time. Since we were staying at AK, we went back to AK two more times (on our break days), so we had more than enough time to check out the whole park. It was so nice being so close to the park!
We just got back January 31st and we didn't actually get to MK until day 6,7, and 9 of the trip. We were done all of the other parks before we even got to MK. I probably wouldn't wait that long into a trip again to hit MK though.