and that's all that really matters
I watched Departed before IA. Both great movies, but the different styles is what got my attention. Departed just focused more on the "rat/snitch" theme while IA focuses on Dante's Inferno. Even though I wasn't entirely impressed by their references, it ultimately made the movies unique and memorable.
My pick would be IA for sure. I think it was a much better constructed story as well as dynamic characters. Leo and Jack did pretty good, but overall the IA cast was much more solid. I just couldn't take Departed too seriously after listening to Mark Wahlberg's jokes, even though they were great.
Marty saw something, he liked it. He wanted to share it with the world. I liked I.A. better also.