Quibbles: in the first one there is some oblong object visible in the mist, more or less a horizontal line in the middle of that soft cloud. I find it distracting, and wish it either were not there, or made itself more obvious (I don't know what it is). The light feels a little strange, the foreground is very dark and moody but the falls and mist seem to be more or less well lit. These feel a bit like looking out of a cave, but I don't think we are.
I honestly have no idea what that oblong object is. It is most likely part of the hydro plant building that is embedded into the gorge wall on the Canadian side of the falls. I messed with the sliders in LR to see if I can blend it in, but that didn't result in anything I liked.
I am fascinated by photographs which rob me of a sense of scale. How close is the stuff in the foreground? It feels sort of like puddles at our feet, but for all I know they are vast pools 100 yards away. This inability to tell scale is a positive, for me.
This was kind of what I was aiming for in the first shot. The foreground rocks are about three feet away, but that is just the top of a 170 foot drop with the pool in the mist below.
I prefer #1 because it encourages me to look deeper/further into the image. #2 is just "there" and that's it.
With #1, I feel there should is something more above the image. There appears to be a falls line in the middle top that is incomplete and the beginnings of a treeline that also feels incomplete - both of which, if included, may give the scene the sense of completion I, for one, am looking for. Of course, perhaps you've done this on purpose, to leave us wanting more!
I was trying to obscure the rest of the falls in hopes of really emphasizing the potential energy in the water (this is what happens when you give an engineer a camera)
That monochrome is great. I might try to play with the shadows a bit and then convert it. I'll post it after I play with it.
Thanks much for your input!