That's a nice fun question - thank you :)
Well, I had no idea, so I did some research. It turns out that the answer to this question depends on... what exactly the question is.
Per cup there's more caffeine in coffee than in tea. Significantly more, in fact - 2 or 3 times as much, on average.
But, per gram, tea comes up the more addictive (with more caffeine). It's just that you use much less tea, in terms of mass, than coffee to make a cup.