Rahat Ahmed’s review published on Letterboxd :
LIFE AS FICTION — In short, The Departed is one of the best American films of 2006, and the best work from Scorsese since Goodfellas. Whatever qualms one may have based on their positive experience with Infernal Affairs, these should be given less gravity due to the meticulous craftsmanship that Scorsese employs in his direction. The film is not perfect (which is a common ailment for most remakes), but isn't so mostly because of certain personal preferences. It is, however, sharply written with an incisive comic pull and drenched in objective emotion.
The cast is flawless (so much so, that the film was recently awarded Best Ensemble of the year by the National Board of Review), with Leonardo DiCaprio giving what is perhaps his finest performance to date and worthy of an Oscar nomination. Mark Wahlberg gives the film an extra edge (and definitively separates it from the original), and Vera Farmiga is a promising, if delayed, discovery. The only weak spot seemed to be Martin Sheen, but that seems to be attributable to the script's momentary weakness rather than the actor's own abilities.
I found it fascinating how The Departed barely felt like Infernal Affairs. While hard not to continuously compare the two, there were more than enough fresh jolts in the Scorsese venture to take my mind away from the original. But as for the inevitable question of which is better, the honest truth, however sidestepping, is that they are different films with different styles based on an underlying idea that alone could not have made these the works of art that they are.