I think Polly has given a great answer. Tracing helps with breadth, and copying (draw from reference) helps with the depth. If you're just starting out, I mean, really just starting out, tracing are a great viable option. You can produce dozens of drawing by just tracing. But as you progress, even though tracing is great at first, you will notice that tracing won't give you much of help when you want to create something out of your imagination (without reference). This is kind of perilous position for artist, because our ultimate goal is to be able to create something out of our imagination. And the other thing is that, as you will grow as an artist, even when you're using a reference image, you will often find yourself not satisfied with the reference images you got. Whether it's the light, the pose, or the proportion, there's just something you don't like in it, that you want to change. If you have only been doing tracing, doing this is nearly impossible. But if you've done your homework studying things properly, changing aspects in reference image that you don't like is an easy job.

I've found from experience that you learn from tracing, but you learn less than you do from copying. I think what you do should be based on whether your goal is to take in a lot of poses/figures fast, or if you want to do a more difficult, longer, and more educational study. Sometimes after I trace things I find that I'm not able to draw something similar (but slightly different) myself as much as I thought I could. Both are good, tracing can help with breadth and copying can help with depth.