We did both parks in one day in October. Granted we didn't do everything
This is exactly my point. These two phrases ("We did both parks in one day" and "We didn't do everything") always seem to go together when discussing Universal. Newsflash: You can do
any park (be it Disney or anywhere else) in under a day if you "don't do everything". Being able to do Universal in under a day doesn't make USF and IOA lesser parks. In fact, it may actually say something about their efficiency.
Interestingly, I was just there in August with my girlfriend and I discovered that August is apparently a very slow time in Orlando. We went on a spur of the moment trip and got a killer deal on our hotel, airfare and rental car. People had told us that it would be slow because they don't tend to have as many conventions that time of year, and also kids are just returning to school. I have to say, that was excellent advice and it was definitely the time to go. We will go in August again next year without question. Our hotel (the Orlando Peabody) was like a ghost town and it's a beautiful, luxurious hotel.
We only had 3 days total, so we definitely had to maximize our time. Since my girlfriend had never seen Animal Kingdom or either of the Universal parks, those are the places that we visited. At Animal Kingdom we arrived about an hour after park opening and left about 2 hours prior to park closing. In that time, we did all of the major attractions (i.e. Everest, Safari, Dinosaur, Kali, Nemo musical, It's Tough to be a Bug), some of them multiple times, and we did most of the minor attractions/shows, and also had time to enjoy a turkey leg, and two sit down meals, plus some quality time just walking around the park and taking tons of pictures. The fact that we were able to do all that in a relatively short time is not a commentary on Animal Kingdom's "lack of things to do", but rather the fact that the park was slow, we used fastpasses, and also the Cast Members' efficiency.
The following day we went to Universal. We got to IOA as soon as the park opened and did Hulk twice (walked on both times). Then we purchased Express Passes, which only allow you to skip the line on each attraction one time. Using the Express Passes, with the parks relatively dead, and only going on each ride once (with the exception of Hulk at the start of the day), and staying until closing time, we still were not able to see everything. Granted, we also stopped and ate at Mythos, which took about an hour from the time we walked in until we left. The only other meal we had that day was a turkey leg at USF. We also did the Universal parks at a somewhat faster pace than we had done Animal Kingdom.
So I guess my point is that when people say that both parks can "easily" be done in one day, I find that to be a bit of a stretch. Is it possible? Sure. But when people accomplish this, I tend to think they are probably racing through, skipping a lot of stuff that they can later come here and post "didn't interest" them, and generally fail to give Universal a fair chance.