This is a personal opinion based on partial evidence, but here hoes. I don't think he's ready to be leading the line in an EPL team with aspirations to challenge on all fronts, based on what I've seen. I think he's more of a Tony Martial back in 2015 type of signing. An explosive and dangerous player but currently not a very well rounded one. One who'll need a few seasons to mature into the role.
If it came down to the 2 then I think Muani's hold up play, aerial ability and vision in spotting (and executing) a final pass are superior and would prove much more valuable to us in the short term. Especially considering our main goal threat is Rashford and so a player who can also feed him, will amplify the threat of our attack. I don't mind signing players for the long term, but we do need a striker who can lead the line now. Otherwise we risk finishing outside the top 4, then ETH gets the sack and we have to start all over again. The long term is never really guaranteed. We have a pressing need for someone who's a bit more ready than Hojlund, someone who can be dropped straight into the starting XI.