No question about it, you can't beat natural sunshine when you want your trains to look real.
I'm in the middle of moving and my layout is in five sections in the basement waiting for the movers to move it into the new house next month. What I think I'll do is before I glue it all back together (ha, ha, glue!) I'll take one of the more attractive sections and have my wife help carry it back out, put some appropriate engines and cars and try some natural sunshine myself. Fortunately the new place has a walk-out, sliding door basement.
God, I'll be glad when the move is over!