G. Mark’s Answer
You are likely to find more opportunities in mechanical engineering, partly because of what you mentioned -- aeronautical engineering is a subset of mechanical engineering, or rather a specialized type of ME. I personally have seen more ME jobs than CE jobs. But the real reason for choosing one of these is more toward your own proclivities. All of these are demanding curricula as well as demanding jobs. But your performance in all of these is mainly determined by which one you personally find most rewarding and basically, fun. You'll apply yourself more in something you simply like. So the easy, obvious, convenient and most fun advice is to simply look into these and see what looks like a lot of fun. Life is better when you enjoy it, right?