Tea contains a greater variety of alkaloids that affect the CNS. Caffeine is a stimulant in the category of xanthines. While coffee only contains one substance in this category of substances, caffeine, tea also contains theobromine, wich is active for a longer period of time. There are some other xanthines present in tea as well, theophylline and theacrine, but i don't know if they are shorter or longer acting.
Theobromine is also the main alkaloid in cacaobeans and chocolate. The effects of theobromine are simmilar to those of caffeine, but not identical.
I have taken pure theobromine a couple of times, and i personally find the effects to be milder than those of caffeine. It seems a less pushy kind of stimulation.
Theanine is a substance that falls in an even completely different category of substances, both chemically as well as pharmacologically.
The effects of theanine are shorter lasting than those of caffeine.