Those numbers are fairly comparable. Foles had the singular fluke of winning a Super Bowl MVP. Not that that means a lot.
The YPA is way better for Mullens and I think it's a very telling stat. And other than INTs Mullens has him beat across the board.
And that's not to mention Foles' stats are inflated by 1 outlier season of 27 TD / 2 INTs and 1 outlier season of over 70% completions (he has 3 seasons of under 60% which is very bad). It's a runaway across the board (other than INTs) without those 2 outliers.
Foles requires smoke and mirrors to even be passable and I don't think we have that here.
All that said, the drawback with Mullens is the INTs but finding a perfect backup is rare. I'll settle for a guy who can move the ball and I'll cross my fingers on the turnovers.
Don't get me wrong, turnovers are a big deal. But what good is protecting the ball if every drive ends in a punt? Give me the guy who can make plays every time.