I just got out to Texas and never had Five Guys or Whatabburger before- they were ok, I have to say though, by far Mooyah is the best new burger place we have tried.
Also I'm from california and IMHO In-N-Out is over rated, they just got one out here in Texas and people are going crazy about it and I'm like "yawn" lol. Maybe it's because I'm used to it and it's nothing specail to me, I dunno. I am excited to try more places out here though, I do love a good burger