I'd be surprised if Gruden was a better recruiter than Butch. A better tactical coach, sure, but for all practical purposes, Gruden has never recruited. Recruiting is a huge part of being a college football coach; totally different than being a pro coach.
I really have no idea how good Gruden would be as a college coach. I wouldn't be stunned if his teams were good, but I also wouldn't be surprised if he had trouble adapting to the things unique to the college game and struggled. He isn't coming to Tennessee anyway, but even if he was it would be far from a sure thing he'd meet expectations here. And if he didn't win the SEC by about year 2, the fans would run him off because expectations would be so high.