I love Old Navy flops, too...
I have not tried on the HL flip flops. I would go with the ones that are cheapest, simply because people tend to look at the design and ribbon rather than the brand. At least that is what I would think.
Maybe you could do some of both as a trial and see what response you get? IDK, just a thought.
Good luck! I have LOVED all of the fops I have seen on this site!