The perfect tense is used to imply relative action. The present perfect continuous tense implies the action is ongoing relative to the present moment.
I am watching TV (this is what I am doing now)
I have been watching TV (this is what I have been doing for some time before now)
Unless you really need to imply the action takes place relative to something else, you should not use the perfect tense.
I am eating potato chips (simple, this is just what I am doing)
I have been eating potato chips all day (relative, implies the action has been going on for some time -- perhaps too long, or too much, or also perhaps that I've had nothing other than potato chips)
Again, the difference is the relative action. If I relate something to the present moment, I can add significant nuance to the sentence. For example:
My son has been playing video games all morning.
This implies that I think, perhaps, he should do something else now.