I like smoke because it is an additional moving, dynamic feature of the toy train that is fun. To me it does not make the loco look more authentic or realistic: I've never seen smoke from a toy train that looked realistic, rolling out in slowly dispersing billows that roil and twist away slowly as do real-world 1:1 clouds of smoke). It's just fun. That said, I seldom run with smoke on, because of the odor, which my wife finds very objectionable even in small doses.
Lee; I think you need a new wife! Or maybe a ventilation fan.
Seriously, I run smoke most of the time running steamers, but diesels not so much.
I just think it looks so much more realistic and adds to the enjoyment. Visitors are knocked out by smoking locomotives. I mean they love the smoke; not that they are overcome and need resuscitation.
Just my .02 worth.
Rod