Wickham started to play well in the Prem, Pelle hasn't played in the Prem atm. So you can't judge if Pelle would be better.
Agreed it's difficult to tell how well Pelle will do in the Prem. Same with Ings. 6 goals in 40 appearances for Wickham at Sunderland is pretty poor though and he's never been a goalscorer. I'd be concerned where the goals would come from without a recognised goalscorer up front as we've been hardly prolific from midfield (Cork, Schneiderlin, Wanyama).