There's a multitude of emulsions available, even after a lot of them have been discontinued. Each one reacts a little differently to light, both in terms of requiring more or less light, but also in terms of reacting in various unique ways to light.
I've been spending a lot of time in the past year or so on finding ways to continue to shoot film, but doing it more economically. The first step was getting my own scanner so I didn't need to pay somebody to print or scan my photos. Lately, I decided that my cost of B&W developing was too high, so I set up my own darkroom
People in the 35mm and digital shooting worlds tend to place a lot of importance on having the sharpest lens and the finest grained film/highest resolution sensor. People shooting 6x7 or large format have far less to worry about. I wanted to try out Kodak E200 to see what it looked like for my next film comparison, since it was freshly-expired in 120 format at the local camera store, but I realized that I couldn't make any realistic assessment of how grainy it was in the 6x7 format. So, after playing with UC 400 in the 35mm format, I decided I wanted to know what it looks like on my 6x7.