First off, Ariana Grande is perfectly fine. She's great. "Break Free" is the gay anthem we've all been waiting for. "Honeymoon Avenue" is, like, totally MY JAM. "Problem" is good even if I can't understand anything she's actually saying.
But there's something completely flawed about comparing Ariana to Britney Spears. At 21, Ariana has had a legit fraction of accomplishment compared to Britney at the same age.