Gasoline vs Diesel generators

Shortly after the CC blew up, my generator failed too so I'm looking for a new generator and for budget reasons can only afford the 3000rpm models. My solar and battery system are both slightly too big for our consumption and since the new year when we moved in, we've never had to start the generator (well until the bl..dy CC blew!). So the use will really be for the rainy weeks in spring - I'm estimating about 300 hours/year max runtime. And since it's only for these emergency uses, I'd just use it to bring the batts up from 50% to 80%, which is 288Ah =~ 15kWh per run. So something like 3kW continuous for 5 hours.
Diesel costs about 30% less than gasoline here, but then a diesel genset costs more upfront. Also, I've been told that the 3000rpm diesels are not that reliable - not matter the make - and that I'd be better off with a cheaper gasoline unit with lower upfront costs, even though the fuel costs more. I really do prefer diesel, but don't want to get a 3000rpm machine that will give me problems down the road. Opinions welcome

P.S. I know a lot of you like the inverter gens, but I'm not considering them because I will always be running the generator at a fixed load during bulk charging only, so no need for throttling to save fuel.