I like the first one. I like the bright color of the tractor and feel the mist comes across better. Also, the sunlight [early morning or late evening] on the tractor is better in the first shot; in the B&W version it just looks like glare, in the first version it conveys a feeling of warmth.
For me the colors in this shot are too good to be converted to B/W!
For the composition - take the second shot COLORED and cut a little bit from down and a little bit from right (to hide the electrical thing), I would like it that way
I think it would be tough to get multiple exposures of a moving subject that will line up perfectly.
I like the black and white, but I think it could benefit from a contrast boost. A nice "S" in curves and perhaps a small bump on the high side of levels would make this image pop more. It just seems a little duller in black and white- is it the same processing as the color and converted?
On the other hand, more contrast would sort of undermine the "fog" part of the effect.