The FA youth Cup squads in general.
If you only look at players who succeed - and not take into consideration how well they succeeded (basically a first-team player and an international are considered equals) - the most successful sides from 1980 to 2010 are:
81/82 United - Blackmore, Whiteside, Garton, Hogg, Hughes and Andy Hill who had a long career including 5 seasons at City
85/86 City -. Hinchcliffe, Brightwell, Moulden, Redmond, White and Lake (Ian Scott even got some matches for City - but just like 20 or so)
91/92 United - no comments necessary
96/97 Leeds - Robinson, Kewell, Smith, McPhail, Woodgate and Alan Maybury had a long career with Hearts and Leicester
97/98 Everton - Jeffers, Dunne, Osman, Cadamarteri, Hibbert and Phil Jevons also had a long career in lower divisions
00/01 Arsenal - Sidwell, Volz, Pennant, Aliadiere, Hoyte - in addition Rohan Ricketts (Spurs and Wolves) and Justin Thomas (Charlton) had long careers in other clubs
02/03 Boro - Turnbull, McMahon, Bates, Davies, Wheater, Morrison (Mostly at WBA), Taylor, Brunt (Mostly at WBA and Sheffield W)
04/05 Southampton - Bale, Walcott, McGoldrick (Sheffield U, Ipswich etc), Lallana, Nathan Dyer, Best (Coventry, Newcastle etc)
I stopped after 2010 because there are still a lot of active players in these FA Youth Cups - so it's hard to compare