I like the idea of glass but the guy at Astro Zap swears up and down that the film is better so I bought one to fit a 6 inch. I need to spend more time on it to decide. I really like this new product being released at NEAF this weekend: Quark by Daystar Love the idea of using any refractor I want to from a 100mm to 200mmm.
Film IS certainly better than 99% of all front mounted glass white light filters (i think zeiss makes one glass filter that is actually very great optically). The only actual exception here for better images than the film is a herschel wedge on an apo telescope.
Also note that you probably could not buy a 30" diameter glass solar filter to fit over those hulkish mirror scopes