Conversions may or may not be better depending on the particular circumstances. In our case, I suspect most of our regulars are already signed up, and/or that the casino website just doesn’t convert what we send, for whatever reason.
I am a fan of Flash under limited-use circumstances as well. I doubt we would carry more than a max of 2 anywhere on the site, and 1 is probably enough. If the size is too big we wouldn’t accept it either.
There are always situations where the Flash banner will convert far better than the ordinary banners – so each webmaster has to really take a lot of things into consideration.