As Rosa said, no, but I'd like to complicate things slightly ) by saying that, "на мои взгляд", more common than either, is *onto* - "Your wristwatch has fallen onto the floor." (My brit. English experience is that of your examples, '...on the floor.' is more common, but not grammatically different. But neither would be used in actual speech. You would probably almost always just hear, "You've dropped your watch!")

No, although the most common one used is "Your wrist watch has fallen to the floor"

Not really any difference, no :) The only thing is that, the words "to" and "on" help in determining where something is. For example, in your first sentence "Your wrist watch has fallen to the floor." it gives us a sense of direction, of Where the wrist watch is Going. Your second sentence "Your wrist watch has fallen on the floor." it lets us know Where the wrist watch Is at the present time :)