Boy, do you have good timing! I'm going to WDW May 13th-22nd. A couple of months ago I bought Teva Pretty Rugged Leather sandals, Teva Mush flip flops, and Teva Olowaha flip flops. I'm not a flip flop person. I never could stand the thingy between the toes, but the piece between the toes on both the Mush and Olowahus are both so soft and turned kinda sideways so they're very comfortable. I thought I had found the perfect shoes for my trip. I wore them everyday to walk my dog and everytime I went shopping to make sure they would be broken in for WDW. No break in time was really needed because they were comfortable from the time I first put them on.
Then I read the thread here about Crocs and just thought they were the ugliest shoes I had ever seen. Then about a month ago, while in the mall one day (wearing my Olowahu flip flops) I saw some Crocs at Hallmarks and some more at Wild Birds Unlimited. I had to try a pair on just to see what all the fuss was about. That may have been a mistake. I bought two pairs that day (a pair of the Beach style and a pair of the Nile sandals). I've started alternating them with my Tevas everyday and now can't decide which ones to carry to WDW. All five are so much more comfortable than any of my other shoes. I usually walk several miles per day, by the way.
If I had to pick only two pairs though it would probably be the Teva Mush flip flops and the Croc Nile sandals. Hey, the Mush flip flops were only $17.99 and the Croc Niles were only $29.99. For that price I would buy both and then decide. The only Tevas I've found that are uncomfortable are the Hurricanes. They're a cheaper model of the sandals and just don't have the support the Teva Pretty Rugged Leather sandals do.
By the way, the Niles don't make your feet look near as big as the Beach models in the Crocs.
I'm anxious to hear other people's replies to this thread, especially the ones who have worn both all day in the parks.