Don't know your academic ability so it's hard to say. But if you've taken it in high school already and did well, then I don't think it's a problem. However, if you've never taken it before, then I strongly, strongly recommend taking one to get your feet wet and get a general sense. Then take the other class later. Also, make sure that one class isn't a prerequisite for the other.
I remember when I was first exposed to macro in high school in 12th grade. Sat in front of the class but had no idea what was going on and ended up with a B- or C (pretty big blow since I was one of those crazy, overachiever students). But when I got to college, I immediately took it my freshman year while the materials was still fresh in my mind and got an A in macro and A- in micro. Curving did help though

I think macro & micro have a bad rap as being hard. It's best not to think those classes are hard but go in with a willingness to learn. Don't listen to the horror stories. Just work hard, and if necessary, go to tutoring or get help from the professors. Then you'll do fine. No different than other classes, really. OK, might be a teeny bit harder, but you'll have some easy classes too, I'm sure