Certainly Man Utd as there is a slightly higher number of higher CA/PA players who will not feature in the first team yet. Frazier Campbell is definately the first player to get. You should also be able to get Evans, Martin, Lee, Hewson, Eckersley (both) to name but few.
With a limit of potentially 4 loanees, I would have Evans for defence and likewise Eckersley, Martin, Hewson or Lee for midfield, (Lee is a good choice as he can cover defensive and midfield positions), plus the *MUST HAVE* striker Frazier Campbell.
You have a loanee in each area of defence, midfield and attack and I find this helps the team gel quicker too, as the loanees already know each other well.
Good luck whichever you choose. Certainly lucky to get a choice of three superb clubs :thup:
This is important because players "likely" to feature in the parent club's first team, will not come to you on loan.