I am not a big fan of this deal
A- Napoli are difficult to negotiate with. They'll take us to the cleaners on this one
B- The Serie A is very different (and easier) to the EPL and most strikers who were great there end up failing here
C- Osimhen was amazing during 22-23 season but he didn't emulate that season throughout his stay at Napoli. His goals tend to come against the smallest sides as well. For example his last season at Napoli he scored 17 goals in 32 matches. That's quite respectable except that he scored just 1 goal against a top side (ie Barcelona). He scored no goals against a top 4 Serie A side. The rest came mostly against the likes of Sassuolo (3) and Frosinone(3). He also scored goals against Cagliari, Monza, Udinese, Lecce and Braga. The only two goals he scored against decent sides were Roma and Barca. Even in the electrifying 22-23 season he only scored 1 goal to a top 4 side (Milan). That's a problem because I reckon that half the EPL table would do well against the Serie A top 4.
In my opinion we should go for Delap. First of all because we're better of spending less upfront and then buy more creative players. That's were the real issues lie in my opinion. Secondly Osimhen has a monstrous salary with very little to justify it. That means that if he fails then we're saddled with yet another player we can't get rid off. Finally the United mess will need time to sort and while Osimhen isn't old he'll probably be in decline by the time we are seriously competing for the major trophies.