Both work great for me! I usually try and keep my tennies on until around 4 PM, then change to Crocs. I like the Malindi style at home and Crocs Capris at Disney. They are flip flops and were wonderful! You have to watch certain kinds of Crocs b/c if they have no ventilation, you can get athlete's foot. I got it in Crocbands ballet flats. Not a major issue though. I just bought an antifungal and now only wear them sometimes, not all the time like I was before. Crocs are great for evenings b/c of swelling in your feet. Even if you can't see it, with the heat and all the walking, you most likely will have it to a certain degree. My family brings both.
Edit: I forgot to say that there was only one way I made it in my tennies. I do not wear them often b/c I don't like feeling confined and sweaty. I had to wear moisture wicking socks! They were wonderful and I never felt sweaty and uncomfortable!