Well, now that I've been challenged, I have changed my mind. I really don't like either one of them
I have always disliked having the gap between the trees and river, because it just looks too artificial and fake. But a second look and I also don't really like having the trees tight to the river.
In my own maps, I have taken to having the river disappear under the trees and re-emerge on the other side. This, of course, conceals the river beneath the forest, but that seems ok to me, unless there is some crucial reason to show the exact path of the river.
One thing I have thought of for carpet forests but never tried, is to have the river disappear under the trees, but make a very slightly darkened treetop shadow where the river runs.
Sapiento, any chance you could try that and see how it looks? You're good enough to make it look great, or to show that it is a stupid idea