Answers :It depends on your individual response, which can vary widely from one person to the next. The hassle factor sometimes lies in the fact that most antidepressants are tweaks on serotonin or norepinephrine modifiers, which require a certain ramping-up period to see if a particular one works for you. That's not an immediate process for most people, although some see a response within a week or so. If Celexa worked once, it may work again.
Weight gain can be an annoying side effect. You have to decide if the gain of any drug is worth its side effects. That can be a mixed blessing when you are depressed. Exercise can seem like a real uphill climb. If you can get a decent diet and steady exercise in hand, you could theoretically find a good balance. Exercise by itself can be helpful, so try to prod yourself into making a habit of it, as it will enhance any other treatment you take on.
If you've had any of them work before, you already have a fairly good idea of what to expect, even with some possible changes over time. If you feel bad enough, its certainly worth a shot.
For a straight-shooting overview of various drugs aimed at mental issues, go to www.crazymeds.com, which includes not only comparisons and links to various resources, but some frank and funny comments from the user's perspective. That can put a human face on it and help you make a more solid decision. Good luck! They are considered close "cousins", and are both SSRI's. I've taken both of them and prefer Lexapro; I gained less weight on Lexapro than I did on Celexa. 