Here are my thoughts.
You won't know the answer to your question without taking inventory of your loads on paper and adding them up. Secondly - how much effort are you wanting to put into this? These are not set-and-forget machines.
As mentioned above once you have your inventory you need to look at what your priority loads are.. Things like the fridge. What can you live without? Do you really think you'll need to run an electric dryer while on emergency power or bake a birthday cake?
In my case I can get by on a MEP-831 (3kw) generator. That gets me lights, water (well pump), TV, and a microwave/convection oven. I cook on gas and my hot water is solar. In this mode I can easily survive on 1-2 gallons of diesel fuel per day. Fuel burn average will be around 0.25 gph.
If I want to run the AC in the summer I would need a MEP802. That will handle the 3T heatpump I have. Fuel burn goes up to an average of about 0.4 gph.
If I want to run the AC, bake a cake, and dry some clothes my MEP803 will do all that at once. Fuel burn will average 0.8 gph.
Where I live when the power goes out for any kind of a weather related event it stays out for 3-4 days. Each of the scenarios above require differing amounts of fuel storage and effort. If I want to fire up the 803 and pretend that nothing happened in relation to my lifestyle in the house that will cost me $30-$40 a day in fuel. I have about 100 gallons for the generators plus the 40 gallons in the truck's tank so I can certainly do that if I want. Not my first choice for sure.
If the weather is nice and I don't need AC I can live very comfortably on $6 a day in fuel running the 831. That minimizes the amount I have to mess around with fuel.
So.. You may say you want all those options but only want to buy one generator.. If thats the case I would recommend that you buy a LP/NG generator. Diesels in comparison don't scale well that way and its not good for them to run lightly loaded for long periods of time. You increase your maintenance costs if you don't run diesel generators loaded. Its best to size the unit for the expected load and keep the load on it the best you can. The way around that issue is to have a load bank and if you run your machine 15-20 hours lightly loaded you would put it on a load bank for an hour or two and run the snot out of it. This adds to the amount of work YOU have to do (and extra stuff such as a load bank) to keep the equipment in good running condition.
For many of us this is a hobby with the practical side of having a reliable source of electricity in virtually any scenario.