Corners are a pretty insignificant part of the game. JWP's corners look good but do we often score from them? In fact, I wouldn't be surprised if the stats of converting corners whether its JWP or Tadic or Bertrand or Davis or whoever taking them were not remotely significant in favour of any of them.
Likewise, how many free-kicks has he scored? 3? I can't be bothered to check but he doesn't exactly bang them in. He might have a reasonably good ratio but, again, it's not very significant in terms of contribution over a season.
Defending. His defending is ok; he tries. I don't think there's much in it. He hasn't got any recovery pace and isn't very strong in the tackle. I know who I would rather have receiving the ball under pressure when we're under the cosh and it's not JWP.
Penalties - yep, Tadic's penalties are bizarre. I'd sooner have JWP. But I'd sooner have Austin than either.
The fact is that when Tadic plays well he is capable of influencing and winning matches at PL level. JWP is just an average supporting cast member.