As stated here:
The future continuous refers to an unfinished action or event that will be in progress at a time later than now.
I found a person who asked the same question as you here. He got a very good answer, from which I inspired mine.
The simple future gives you one information : the action will occur in the future.
The future progressive gives you the same information, AND it also tells you that the action will be in progress.
"Tomorrow at nine o'clock I will be watching TV, so don't call me."
This sentence tells you that the action of watching will be IN PROGRESS at nine o'clock.
So to conclude, I will quote the person who answered the question I linked:
If you simply want to state that the action will happen in the future, you can use the simple future.
If you would like to say that the action will happen, and you want to emphasize that it will be in progress at some time, you can use the future progressive tense.