Tea definitely. Tea has proven health benefits whereas coffee has lots of caffeine which is pretty notorious.
For me I can have tea without sugar but not coffee. So tea is healthier for me.
Tea has caffiene too, which is why it's addictive. It usually has less than coffee, but it depends on the variety. I read somewhere that coffee can help stave off the effects of dementia, though its' been a while so I'd have to go hunting for the article. Caffiene can help people with ADD or ADHD as an alternative to ritalin. Tea has antioxidants, more in green tea and white tea than black tea.