Hey, my name is Tim Black, current Guinness World Record holder for Fire Breathing. I just stumbled across this thread today :)
When performing the fuel I use is a hydrocarbon solvent called Shallsol T, TD or TK, Isopar L of G, or Pegasol 3440. These are all variations of the same thing, with slight differences such as flashpoint etc. If I'm attempting to break a record, I'll choose the fuel I use based on it flashpoint, taking into consideration the temperature and humidity of the environment I'll be making my attempt in. Never use a fuel with a flashpoint below approx 40C for fire breathing though.
With regards to what you said about fire eating, I never use fire eating in a show. As you suggested, it's more dangerous and far less impressive to the audience, and so that's a tradeoff I'm not willing to make. I suppose it would depend on the audience or type of show you're doing, but for me, it's not worth the risk.
Tim Black
Androgen Fire Art
www.androgen.net.au