Hi Eud...
I feel that in the price bracket your looking at there is not really going to that much to choose between machines. You've not exactly set yourself a very high budget at ~$40.
Strangely enough though, before I splashed out on a nice Look Solutions Unique 2 Hazer I had a couple of different 'cheap' smoke machines and they were both surprisingly good. Well, they were good for home use on an occasional basis. There is no way a smoke machine at that price will last long in a commercial environment.
Sorry I can't be more specific, but I would just go for one and give it a shot.
Cheers
Jem
Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001