As fast food burgers go, both are usually okay. Seems like Whataburger tends to use more onion & mustard than most though.
I like extra mustard on mine!
Plus, using the app, and answering a simple survey on my phone, I get a free burger, with fries & a medium drink for @ $6.20. (Not to mention the freebies from the "points" on the app).
Whataburger is a good deal for me, & it reminds me of when I was poor...keeps me humble...