Stump!!! I like how it balances the top left cloud and its reflection and how it adds interest to the lower right area. The alignment of the stump with the top of the cloud reflection, and the overall height of the stump leaving about the same distance to the shore line as the top of the cloud, (non reflection), leaves to the top edge of the picture. To me that makes a much more balanced image.

That being said though, if the intent is for people to focus on the cumulus cloud and its reflection the the top image fits that better. I find myself only seeing the cloud and its reflection, not the rest of the picture