Which is more effective: bupropion or celexa (citalopram)?

Depends.: First, each person is different and one might be better for one person and not another. Second, Celexa (citalopram) is a brand name and bupropion a generic. In general Wellbutrin is more effective for depression than Celexa (citalopram), but it has no tranquilizer effect which Celexa (citalopram) does. Some generic bupropion is not as effective as another.

Not that simple: Celexa (citalopram) is an SSRI antidepressant which can be very effective in treatment of anxiety and typical depressive disorders. Wellbutrin (bupropion) is very useful for treatment of smoking cessation, atypical depressive and seasonal affective disorder symptoms