You have Mainoo who is an outright star as a very progressive 8. You play with Bruno who is essentially a 10, but likes to roam and is very attack oriented.
You are signing one of the ELITE defenders, but he is still very young, and you are highly likely to pair him either with Licha (who is excellent … but still size challenged) or so wind completely new to the team (where the coordination with defenders could be off)
You are not set up to play with a regista instead of a DM on top of all that.
United need an imposing physical presence, who is also composed on the ball and be a reliable outlet that can get the ball forward.
Those are rare. Ugarte would do SO much to tie the team together as a shield for a young defense, a master of the dark arts as well (which is an underrated quality), and still provide a very good technical midfielder. I watched him destroy Bruno and Brazil’s attempts to play through the middle.
Compare that bringing a very small player with questionable defensive skills, seems a ton younger than Ugarte (but isn’t), and ideally wants to be a deep tempo controller (which requires inverting someone to play next to him at the very least… which would change the shape of your teams play)
It doesn’t seem like a hard decision to me.