Generators--LP or Gas?
Unless the generator is only for occasional use. Propane won't deteriorate or leave as much gunk in your generator as gas. Also, it's cleaner burning (less pollution).
Or unless you already have a large propane tank sitting around or are installing it in an RV which has a propane tank but no gas tank.
On the other hand, if you run a generator on propane you will get less power (or less gas efficiancy) than with gas. Plus propane generators tend to cost more.
One option is to do what I did - get a good gas powered generator and add a conversion kit for propane. Now I can use my big propane tank, or disconnect it and use gas - best of both worlds.