Thank you for your input. The Generacs are crap........after the comments here I will stay away from them.
I have a natural gas supply (installed last summer) and I bought a 500 gallon propane tank 5 years ago. I would really like the propane gen set cause if by some far chance that natural gas service was down and out I would have my own steady supply of fuel. (with home delivery) with diesel and gasoline you cannot get home delivery. A diesel genset would be a wet dream but with the fuel used for a 15-20 KVA the cost would be real high, and having to transport 20+ gallons of off-road diesel to my home everyday would be a major PITA. And, spending $ 12,000 on a diesel gen set for the power going out a few times per year would be a pizz poor investment.