IMHO closed file is good if you don't have a lot of things to talk about, if you've volunteered/done research only a little then this is nice because you can take up time w/introducing each activity and describing it
open file is good when you have lots of stuff on your resume. the interviewer can pick what interests him or her and discuss that. if you have alotta stuff you'd like the interviewer to know but the interview is closed, then you don't get to everything. with open, you at least know that they're aware of everything on your app even if you didn't get to discuss it w/them
overall, i prefer open, i'm just not sure if i like them having the stats....