Joe is correct. I wasn't in the mood to write a book, which is why I suggested researching other posts on the subject (battery power).
If I were doing it, I would sell the 3 rail and buy 2 rail stuff, unless it was an engine I absolutely loved.
I do think RC battery power is the way to go, and it is only going to get better.
If realism is your goal, I would definitely go 2 rail.
And yes, Joe does nice work!
Simon