Its obviously pointless for me to say "I'd prefer our U23s" but I do think most neutrals would agree.
Jackson
Enzo
Caicedo
Fofana
Colwill
Palmer
Madueke
Gusto
Or
Manoo
Yoro
Garnacho
Rasmus
Diallo
Zirkzee
Collyer
Ugarte.
Some very good players in both groups of course.
Both are very promising groups of players, but I think the level of talent and rarity of profile United would have trouble finding and/or attaining, that Chelsea already have in their U23 group, is only Palmer. And that's because he's not only one of the best right wingers on the planet, which is an unsolved position for us arguably since Ronaldo left in 2009, but also because he would be a great long-term replacement for Bruno at #10, or a great right-sided #8 in a 4-3-3.
The others are promising, and some of them pretty good already, but the talent pool in their position/profile isn't scarce. i.e your centre backs in Fofana, Badiashile and Colwill, or your double-pivot DMs like Caicedo and Lavia. Or how Gusto is really good, but United don't really need a right-back right now.
With United, I feel that Mainoo, Yoro, and Hojlund are all rarer and therefore more valuable profiles that we would have trouble replacing if it came to that. Potentially Garnacho as well, but I'm not sure what to expect from him and he often confuses me regarding what his potential ceiling might be. Overall I don't think he's as talented as the other 3.
Mainoo is one of the best midfield talents in the world, and most of the similarly elite talents in his position and age group are already playing for other top clubs (Zaire-Emery, Neves, Bajcetic, Bergvall, Gray, dare I say even the likes of Camavinga, Tchouaméni, Gavi, Pedri, etc. (although I listed different types of players here and Mainoo is arguably inferior to some of them)), and are therefore unattainable. Wharton, another elite talent and rare profile, will get snapped up by a big club soon as well, hopefully us.
I consider Hojlund one of the only U23 strikers in the world that have a 30+ goal/season threat in them. The others that come to mind are Endrick, Ferguson, Omorodion, and Sesko, but I might be forgetting some players. With Endrick and Hojlund already playing for "final destination" level clubs, the talent pool gets even smaller. And yes, I do rate Hojlund higher than Jackson, but his stocks are fairly low now, so I know not many will agree with me on this.
Yoro is probably the biggest CB prospect football has seen since van Dijk himself, with arguably only Saliba being similarly talented to him as a teenager, in the last few years.
Also, I see you mention Estevao and Páez in another post of yours. Two outstanding talents without a doubt, they'll probably surprise a lot of people, but it brings up another issue for me. Where is the pathway for all these talented players? Just looking at the right wing position, you're gonna have the two South American kids turning 18 before the start of next season, on top of Madueke, Neto, and Palmer, who can all play there. Yes, some of them can play other positions too, but how can you give all 5 of them enough playtime? And then, if Neto plays left winger for example, then you'll have Sancho, Mudryk, and Félix all sharing the remaining minutes? You need depth, but this is way too much of it IMO. Estevao, Paez, Palmer, Neto, Madueke, Mudryk, Sancho, Félix, Nkunku for 3 positions? And that's before another spending spree that might happen in January/next summer?
ouch
