Playing for Manchester United and playing for Ipswich is an entirely different proposition for a forward player.
How would Hojlund look in that McKenna team? Rasmus has got sufficiently better players around him and is still way below par.
The other side of that coin is the pressure of playing at United is infinitely more than playing for Ipswich. This as we've seen lately, can have a negative effect on a players confidence and ability to score goals. Delap strikes me as the sort of player one adds to a big club to compliment an already successful striker situation (think Alan Smith or Chicharito), instead of asking them to be the primary contributor of goals. That is potentially, a massive recipe for disaster.