In a sufficiently large RV, an installed generator can be unobtrusive, unless the surroundings are very quiet and you're really looking for something to object to. They also are rather expensive to run, so an electrical hookup should be the method of choice anywhere possible; and few of the monster RV users I've met will willingly run their generator if there's any another choice.
Some people attempt "external add-ons," but these are as obnoxious as any simple "portable."
Few portable generators can run for more than 5 to 8 hours without refueling, and consume anywhere between 6 and 10 gallons of gasoline (petrol) during that time, so about a (US) gallon per hour to have electricity isn't insignificant. (With our ridiculously cheap gasoline, $3/hour = $72/day if run continuosly.) The cost per "energy unit" is pretty comparable for gasoline and propane.
Built-ins will normally use propane, but require enormous tanks to support running continuously for even a full weekend, although I've "heard of" a very few able to run for a week at a time. Those are for people who leave granny knitting in the camper dockside while they cruise on their 60 foot yachts.
Claims to the contrary are total BULLSHIT: there is NO such thing as a "portable" generator that will not cause some imposition on others in most camping sites. Especially with gasoline/petrol fuel, they also smell pretty bad.
Those who say "my generator is so quite it doesn't bother anyone" are probably using it to run their TV for the obligatory football game, so their own screaming and yelling (and paralysis of the senses from the booze and junk food being thrown about) blocks them from noticing that all their neighbors are being significantly inconvenienced. But of course they wouldn't be "football fans" if rudeness mattered? [note: sarcasm?]
Those who require power and might have no alternative to generating their own should accept that they are imposing on others, and should evaluate the extent of, and make every effort to minimize, the imposition. The rest of us should make every effort to accomodate their "necessity," but it has to be a real need, and alternatives must be considered and used when available.
But then, that would require that we eliminate all the slobs from our society, and there'd be few of us left I suppose.