Every branch of engineering has its cycles, you might even say that any area of employment has cycles. However, the good engineers always seem to find jobs (during the NASA retooling period around 2004 when they were cutting programs left and right; my company laid off a few guys at the bottom of the rungs and put a lot of us on burden accounts just so we would be there when NASA came calling again, and they did). It is those same good engineers that seem to make the most money.
So, from what I have seen, it is not what field you are in but how good you are. There is also a strong correlation between being good and liking what you do.
My advice, choose a field that you like and you’ll do all right.