How do you mean? I can understand how some applications would be significantly better than others, but it seems like it would be pretty hard to use something like this (without getting caught) and have it take away from the magical moment or the effect.
Once again, Steerpike put it better than I could.
However I'm going to try anyway.
Smoke is really cool - but it needs to be used at the right point, and not so often it gets old. Less it more. What our spectators imagine is happening is probably better than anything we can actually show them. Therefore, if you use the smoke too often or when it doesn't enhance the effect more than not having it will allow them to imagine, it will fall flat.
It's easy to use these things wrong. Much like it's easy to perform magic at the wrong time or too much.