Hello
The first one has the sun and sky being blown out and drawing the eye away from the falls. The slow shutter speed to blur the water motion is good but it's overpowered by the sun and sky. As for composition. The first thing I'll say for any shot with water; the horizon
has to be level. It's slightly tilted down towards the right. The second one is strongly tilted down to the left. If using PSE there is a ruler tool that makes it a snap to fix. On the first image the curve of the falls work but there is a large area on the lower right that is fairly large but with nothing to hold your interest. For the image as it stands I might crop it down. If you had the chance to go back when the sun was below the horizon so you would have color in it would be better. I might try some different angles if possible. Perhaps a little bit downstream from this spot and maybe closer to the edge of the water. The second one has a much better sky. Apart from the horizon I would smooth out the luminance noise in the sky. The trees, rocks on the lower left help to frame things. Perhaps getting a bit lower and having the shoreline extend all the way across the bottom might frame things better. As a suggestion I would say take the first couple of shots of whatever it is your photographing but then ask yourself what is it that I like about the scene and see if there is a different angle, aperture or shutter speed that might make it better. Sometimes just a few feet left or right or getting higher or lower makes a huge difference. I did a quick edit to show the crop I chose on the first one and tried to smooth out the posterization in the sky. On the second one I straightened the horizon, took out the noise, and a couple tweaks of tones in the lower part to show what I mean.
Posted them here.
http://www.flickr.com/photos/69407470@N06/9649302149/lightbox/
http://www.flickr.com/photos/69407470@N06/9652559226/lightbox/
Regards
Greg