I do both as well. I started out doing the visualization as if I was infront of myself. Now, I only do it that way if I'm not paying attention. So normally, I visualize it right in my body.
I have a strong preference doing it in my body. In fact I've spent time moving it around in the locations. I can't say I've noticed a different for all the centers, but I've definitely found a big different in the precise location of a few of the centers.
Now don't go obsessing over getting it in just the right spot.
Relaxed focus is far more valuable than going energy center hunting.
You are perfection,
Iam2