Do your homework

Hopefully, you've got a battery bank. If not, you're throwing your money away no matter what generator you use. A generator needs to be run at the peak RPM range to run most efficiently -and it needs to be sized to the job. So, to do this - you need to operate most of the time off a battery bank - and when it gets low - run the genset at peak power until the batteries are charged and then shut it down.

How are you going to charge the battery bank? Most portable generators only put out 140 - 150 volts at the peaks of the cycles. Grid power is 170 volts at the peaks. Due to this - conventional battery chargers do not work properly on most gensets. To correct, you need a generator that does make the proper current - or - use a special 10-15% voltage corrector - or - use an electronic battery charger like an Iota.

In addition - if you have an inverter/charger - many of them do not accept power from most gensets. A Trace/Xantrex mod-wave DR unit doesn't. A Trace/Xantrex full-wave SW type does.
A full-wave Outback systems usually does not.

I know many off-gridders that have wasted tons of money on bad gensets based on bad advice. It's expensive to learn the hard way. Most people in the off-grid business have lists of which generators work well with chargers , and which ones do not. Also keep in mind - that many gensets will void warrantees if hooked to an off-grid cabin or house - read the very small print.

A DC generator works best if all you need it for is battery charging. I have a 4000 watt powered by a Subaru gas and propane unit. I rarely use it though - it's basically for backup. If I had to make power for many hours - I'd use my diesel.
Many off-gridders make their own from DC auto alternators and five horse engines. The 4000 watt gensets with multi-fuel Subaru 8 horse engines can often be bought brand new for $300. The market was flooded with them awhile back due to a Telecom company that went under and had hundreds of them, brand new, in storage.

I've got three places on solar - two off grid, and one grid-tie. My small cabin in the woods (off grid) has a 1000 watt solar array, four deep-cycle batteries to make a 12 volt bank, a Trace DR2400 inverter/charger, and a 5 horse DC generator and the system works great. I've been building up there for two summers. I run power tools, my wife watches TV, etc.

In regard to fuel choices - propane is very inefficient. For your dollar - you get the least engergy from propane, more from gasoline, and more yet from diesel (especially off-road diesel).
Many people like propane anyway because it works well with an auto-start system. Diesel in cold areas can be a real problem. I own property in the Michigan UP and live here in central New York. It gets colder here - sometimes down to 35 F below - so I'm well acquainted with it.

I'm curious to hear exactly what you are using the genset for. I've worked on many off-grid systems and might be able to point you in the right direction.