Depends really on what you take with you. If you like your TV, laptop , smart phones etc then you need electric.
If like us you take none of the above then you can get by with just using gas.
I used to have a small caravan and got by very well with just a leisure battery which I charged at home and calor gas. I think if I had a caravan capable of using mains electric I would go for it...not much point in not using all the home comforts you have available.
We prefer to cook and heat the van on Gas, but we need EHU for medical reasons and so have electric anyway and therefore have our lighting on mains.
Also early and late season caravanning requires us to have some heat on overnight and so we have a 600w small oil fired radiator. This is totally silent and thermostatically controlled.
Quote: The only thing I would like and so far cannot find, is a 12v dish washer!!!!
My wife has found a self powered, sink seeking model with built in drying and caddying facilities - namely ME :(