I don't think I could make a recommendation without knowing more because it depends somewhat on degree...bipolar is rather loosely used. Both of those medications have been used effectively, and if your doctor chooses either it will depend how you tolerate the dose and the side effects.
I'm taking 150mg/day of Zoloft. I've started to take it the last year, in November, and probably I'll continue for another 1 year. In these months, since I've started Zoloft, my mood swings up and down, not only because it's a side effect of zoloft, but also because I've drank a lot while on zoloft, and alcohol interacts with the drug. Firstly, mi psychologist diagnosed me with maior unipolar depression, but after 2 months of antidepressant my mood changed with ups and downs, with a possible hypomania. So, I've taken Depakote (valproate) for a week, but i can't stand its side effects, and I've stopped it after a week. In spite of it, today i'm not depressed nor bipolar.
My suggestion is: if you're not severe bipolar (i.e. mania followed by depression and viceversa) don't take any mood stabilizer. Try to wait another 3 months, and look what happens.
Lastly, lithium is not the best. If you can, chose something like Depakote....or, at least, something that you'll not take for the rest of your life (i.e. Lithium).
i am not a medical professional of any type, just someone who suffers from a soft bi-polar disorder. i have been on over 8 antidepressants over the past 8 years with no help to my depression. i am now off all of my antidepressants (since i was recently diagnosed as bi-polar and understand that bi-polars should typically not be on antidepressants, except possibly as adjunct therapy) and will never go back. i am on a mood stabilizer and benzodiazapines, to which they have (perhaps just temporarily) added another mood stabilizer for anxiety. bi-polar brains, even if you spend most of your time depressed, are not the same as uni-polar (depressed) brains. and the former comment is correct - lithium is not the best to treat bi-polar depression. lamictal (lamotrogene) is rated as #1 by the APA for such treatment.
I was diagnosed as having mild bipolar 2 a few years ago. I've tried a variety of meds and I'm currently taking lamictal as a mood stabilizer and wellbutrin to help with the depression side of bipolar. I've been on this combo for a couople of years. It takes a while to get the dosage right with lamictal b/c you have to work up to your dosage slowly in order to avoid a potentially fatal rash (although extremely rare, especially in adults). It's working really well for me and I finally feel 'normal'. I still experience all emotions but on a very manageable and reasonable level. I've only had one manic episode which was a year and a half ago and have mild bouts of depression a few times a year. Good luck!