Congrats on getting a nice fish. You never, EVER want to do a fish mount from the actual skin of the fish. It is impossible to tan them, and once painted, they quickly begin to shrink, move and change on you. I'm sure you've seen old fish mounts that look ancient, it's the same with new mounts.
The copies are perfect in every way and when properly painted, impossible to tell that they are not real. It's all up to the skill of the person who does the painting.