Completely agree with this, wear shoes that your feet are most comfortable with. Flip flops may definitely not be everyone's first choice but for me, I wear flip flops every day and trying to wear anything other than flip flops to walk around in and stay on my feet all day causes so much pain. I would definitely suggest multiple kinds of shoes though just so you can see what works best for you. Flip Flops and Tennis Shoes for sure just to have two options.
For those of us who wear flip flops more than any other shoes, sticking with what our feet are already used to is better, in my case anyway. I wear flip flops every single day. I will put on a pair of tennis shoes occasionally. Last trip, I took both flip flops and tennis shoes because I know the tennis shoes will give me more support but by the end of the day of wearing tennis shoes my feet were killing me. The next day and for the rest of the trip I put my flip flops back on and never had a problem other than the occasional tired feet from walking so much. I would still bring more than one pair of flip flops and also my tennis shoes just in case but the flip flops are much easier on my feet.