A summary on an article from The Guardian by Rob Smyth (2008):
It is harder to distinguish between his three genuinely great sides (1994, 1999 and 2008), but the differences are fascinating to observe. They each have wonderfully distinctive identities: the uber-masculine pack of 1994, who kicked seven bells out of opponents and then nailed seven pints in blockbusting post-match sessions; the intrepid voyagers of 1999, ingenuously exploring uncharted territory; and now 2008's loose-limbed, cosmopolitan collective.
In 1994 they had Le Dieu (Cantona?), in 2008 the Holy Trinity (Rooney, Tevez and Ronaldo). But in the 1999 they had perhaps the highest power of them all: Roy Keane (yes, we know he was part of the side in 1994, but in those days he was a different player entirely). All three scored 80 goals in their title-winning campaigns (1994 was from 42 games). Yet in 1994 they conceded 38 goals; in 1999 they conceded 37, this year it was only 22.
The relationship between attack and defence has certainly changed. Domestically at least, the 1994 side was very hard to break down, whereas the 1999 side emphatically prided themselves on scoring one more than the opposition. They scored as many goals in the Champions League group stages (20) as the 2008 team did all season. But they conceded more in the group stages (11) than this side did in the whole campaign (six). The class of 2008 got to the final on the back of five straight clean sheets, a reflection of the modern ethos.
Ferguson's great sides reflect the evolution of English football; it is a mark of his genius that he has been able to mix the austerity that is woven into the game's fabric with the enlightenment that came with the gentrification of the game in the 1990s. That development left most of Ferguson's managerial peers - George Graham, Graham Taylor and Kenny Dalglish among others - as dinosaurs.
Such change, and the consequent challenge, sharpened Ferguson's taste for the tactical battle. If his first two great sides were, for the most part, sent out in a straightforward 4-4-2 (or, if you prefer, 4-4-1-1) formation, this team (2008) has no real shape, and in many ways the formation is a 4-6-0. Similarly, just as you could pretty much pick Ferguson's best sides in 94 and 99 - nobody has a clue now. The side that started the Champions League final had never played together before,
It didn't help that United missed their main man, Eric Cantona, for much of the 1994-95 campaign (the 93-94 European season was over in the blink of an eye, making it hard to draw conclusions). A talismanic figure, without whom life was unthinkable, has been the essence of each side. Cantona's swagger, class and work ethic not only catalysed the 1994 side but pointed the way for the younger members of 1999 side; when he was banned for five games in the 1993-94 run-in, United's season nearly fell apart. Keane was the endless well of mental strength into which the 1999 side could dip in times of trouble. And now there's the remarkable Cristiano Ronaldo, with his 42 goals, of which an amazing 18 have been the opening, tone-setting goal of the game.
For Ferguson, each will have provided a different pleasure. In 1994 there was the thrill of the breakthrough; in 1999 there was a fatherly pride, yet this probably gives him the greatest satisfaction, because he has shown he can achieve things the European way. And, more importantly, because it's the most recent.
Le Dieu or the Holy Trinity? Which is Ferguson's vintage team?