Tea has less caffeine than coffee, but also has l-theanine, which has a relaxing effect. I've never really been much of a coffee drinker though, so I can't compare the two on a subjective-experience level.
The reason I like the fancier teas is mostly because they have better, more complex flavors and smells. That plus the caffeine and l-theanine puts me in a good head space to focus on whatever I need to.
Tea does it for me. Especially fancy Chinese teas.
I got the challenge a few days before you posted this and haven't heard anything yet, but I also haven't finished the level 5 problem yet.