There isn't too much more added with a 50AMP trailer system. Usually the big deal is the second Air Conditioner.
Also since more folks use the 30AMP connections the camp ground pedstals are more often pretty much wore out so using the 50 amp connection is much cleaner.
If I had a bigger trailer I don't know if I would add the 50AMP service to gain a second air conditioner or not. ALot of folks will install a low profile 9K BTU or smaller second air conditioner and run it direct from the camp ground 20AMP pedestal connection???
I always run my oil filled 1500WATT 120VAC heaters from the camp ground 20AMP connection when I can.
Kinda depends what you want to do camping I guess...
Roy Ken