Correvt me if I'm wrong, but I think the point Clrnc is trying to make is that United, regardless of whether their strikers are better than ours or not, tend to play young teenagers more than we currently do.
Now some consider Arteta to not want to play any kids even at the end of games we're winning or dead rubber games. Others consider our levels to too high to be playing kids and that it would be easier if we were not challenging for the title, which also makes some sense (even though I still think we could be giving them minutes off the bench in some of our bigger wins etc).
Either way the consensus is that there is no way he'd get a chance here, at least for a few years. At United, with the lower expectations than we have, there is much more scope to giving players minutes when their first choices aren't making an impact.
He's still very, very unlikely to get any real minutes there, but I can see why he'd think he has more of a chance there when the likes of Nketiah, ESR, and other established players hardly play, let alone the likes of Nwaneri who is much higher rated than he is and still probably won't play any real part this season. Plus the double wages won't hurt either.