I think that
#118 is better, but the difference is in very subtle details and after you asked me at first I didn't even remember what they were. The gunsite is one and another is a bit bolder outline on the elements in front of the gun in
#118. If you can't spot the difference, I'd say go with
#118.
As for putting it on black, most of the elements are the same, but for example the laser ray on white is a red-white gradient while on #121 it's a red-black one. But anyway if you choose my design I can give it to you both on black and on white.