B.D.
I recently was looking into HRM's and wondered the same thing whether I would rather have a Bodybugg. After looking at the website, I decided that I was not spending that much money for something that was only 80% accurate. Plus the Bodybugg doesn't function as a HRM which I was ultimately looking for.
As for Polar it is the consensus that they are the gold standard when it comes to heart rate monitors. I don't believe your trainer is getting a kickback because I have asked around and have received endorsements of Polar from people with nothing to gain from it.
I injured myself and have yet to buy one but I will be buying a Polar when I am ready.