I make a distinction between "younger Al Pacino" and "older Al Pacino" in terms of his performances.
The "younger Al Pacino" (i.e. Al Pacino in films he made during the 1970s into the early 1980s, in films like Panic in Needle Park, Godfather 1 and 2, Serpico, Dog Day Afternoon, And Justice for All, etc.) was an actor who gave restrained, well-modulated performances, demonstrating his versatility as among the finest actors of his generation, and deserving of every praise he's been given.
The "older Al Pacino" (i.e. Al Pacino in more recent years, perhaps starting around Scarface, and continuing onwards, but is especially apparent in films like Devil's Advocate) is an actor who often resorts to over-the-top overacting. The more restrained version of his younger years do re-appear occasionally, in films like Donnie Brasco, the remake of Insomnia, in certain scenes of Scent of a Woman (excluding the last scene), and in Glengarry Glen Ross, but these tend to be the exceptions rather than the rule. Admittedly, Pacino's overacting can be fun to watch, but it dismays me to see this in his performances given that he's capable of being so much more as an actor.
