The first time I watched the film Andrew Garfield actually left the biggest impression on me and I was little cold on Jesse Eisenberg's portrayal. Watching the film again though switched things around with Eisenberg's performance left the best impression, and Garfield weakened for me. A strange occurrence sure but watching Never Let Me Go the other film he received praise for made me understand a little bit of why. In Never Let Me Go Garfield gives an emotionally charged performance, but frankly too emotionally charged without the proper depth of character to really make the emotion resonate. His breakdown in that film left me completely unmoved because he just did not build to it well enough.
I do believe his performance in this film is better than his performance in Let Me Go though, but it shares the same problem where he gives an excessive emphasis to the emotional state of his character. He puts too much at once limiting his ability to play through the scene properly, or to powerfully build the fears and insecurities in Saverin as he sees Zuckerberg slowly edge him out. I don't want to sound to negative as I don't think he is bad at all, I just don't think he is great. He still does put on a great deal of effort and he does bring the emotions needed to his scenes even if he he takes a little too earnest of approach in his portrayal of Saverin who is suppose to be the moral center of the film.
There are plenty of things to like about this performance still particularly his chemistry with Eisenberg which finds the difficult connection between the two by having a genuine friendship there but as well a distance there due to the conflicting natures of the more self absorbed Mark, and the far more open and modest Eduardo. They are quite effective in creating early on both how the two would work together to make Facebook but as well create the seeds of the rift that would slowly develop between the two. Eisenberg and Garfield both handle this incredibly well by having the vastly different styles of performance that still work together in the same scene.
This is not a perfect performance as his character's arc would have been all the stronger if he simply eased up a little on some of the earlier scenes in his performance. Garfield though is very good in the final payoff scene for his character as he confronts Mark and Sean for betraying him. He delivers absolutely in this scene portraying the righteous anger in Eduardo for what they did to him. Yes this payoff would have been even greater I think if he slowly built up the vulnerability in Eduardo to this point, but as it is it still is an effective scene. All in all Garfield is quite good in his role, even if he does not stand as the best performance as the film.