If you're actually interested in tea as a drink to enjoy, I'd highly recommend looking further into it. Try researching premium teas from China, Japan, and Korea—there's some really phenomenal stuff out there. I've been a barista for six years, so I'm never going to stop drinking coffee, but I've been drinking seriously good tea for about a year now, and I find it MUCH more suited to staying awake and alert for longer periods of time (and it's way healthier than coffee, or soda, or energy drinks).
Thing is, there's actually more caffeine in green tea than black tea in a lot of cases. That's probably the biggest misconception about tea out there. Green tea is the least processed of all the different kinds of tea (red, white, black, oolong, fermented), and thus retains more of its natural caffeine content. There are some exceptions, but in general, green tea has the higher caffeine content. There are other factors however, including the grade of the tea, and the amount of time you brew it. And it should be noted that I'm talking about quality stuff, not Lipton or Celestial Seasonings. I either buy my tea from a local tea house (that buys straight from China), or buy straight from China myself when I have a big enough order to justify the shipping cost.
If you want to stay awake and alert (and like the taste, which is another matter altogether) for longer, without crashing, I'd go for tea, or even maté. It's healthier than binging on energy drinks and sugary coffee too, the downside being the taste, which can be intense for some.
Also, and it depends on the roast and a whole other set of factors, but some teas can have an equal or even greater amount of caffeine than coffee.
TL;DR—tea is healthier to drink, tastes just as good as coffee, especially in the evening/night (tea seems less aggressive than coffee to me, which is suited well to certain times of the day), and you don't crash.
...But coffee is still really good, damnit.