Both me and my wife are devoted coffee-addicts, but tea takes a great part in our lives drinking habits too. I conducted a special mini-interview with my wife asking the same question: when its time for a coffee instead of a tea? (in the photo below you see her recent purchase: favourite tea cup in Chinese-style).
We share the same opinion most of us developed in this thread, about coffee boosting activity, charging energy for the day activity, and so on. 😎 So, what is difference? we dont take coffee 'on the run' and many times per day, just once or (rarely) twice. We prefer to have our coffee when we dont rush anywhere, just sit back and relax and sip the coffee leizurely, spend 15-20 minutes with it. In other words, we set aside a time for drinking coffee when nothing can distract us from our cup. You may consider it a sort of sacred ritual, and you will not be far from truth.
Besides that, personally speaking - I prefer coffee with pastries :P so, in emergency case I go out to the local bakery to get some cookies to go along with coffee, otherwise I may even prefer to skip coffee at all.
As for the tea, it is far less a ritual thing but much more functional; whenever we feel body's dehydration levels increased and it is necessary to replenish the lack of water, we make tea - 4, 6, 8 times a day? I dont count. The two most common types of tea we constantly replenish our stock are: black leaf Jian-hong tea and Nargiz Chilka black tea (it is apparently the same as Dargeeling). They are ordinary grade but high quality tea, true 'middle class'.
Also, sometimes I make tea simply to warm myself - thats why I prefer black tea especially during cold seasons, and green teas (oolong, jasmin etc) in summer time.