Well, I’m a pretty serious dog guy as you might have guessed by my screen name.
With respect, I think you are asking the wrong question. What you should be asking is what is the most appropriate breed for ME (my life style, my family, my energy and exercise level, etc) and not what breed is best for RV’ing. IMO, any well bred, loved and well-trained dog will love RV’ing and can learn/be trained to be part of the joy and no kind of problem.
Obviously, there are many different breeds of dogs with vastly different characteristics in terms of size, temperament, activity level, etc. Since I don’t know you, I would not presume to suggest what breed might be best for you, except to note that you say have had good experiences with Labs, so why not stick to that breed?
For what it is worth, I have had Brittanies ever since I was a child. Since I work part-time as an upland hunting guide, mine are working dogs as well as house pets. Brittanies present a wonderful dichotomy – they are gentle, loving pets who live to please their masters; but yet they are awesome predators and stone killers in the field. To stay mentally and physically fit, they should be run hard off lead every day – I am talking about miles - walking them on a leash around a campground does not count. Brittanies are not for people who are adverse to lots of exercise, or who want dogs that just sleep at their feet all day. At home, we have a good bit of land, so it’s easy for me to run the dogs every day. When on the road, I must sometimes be a bit inventive to find places to run, but many of our trips are for bird hunting and running them is a non-issue
My wife is handicapped and cannot handle a “real” dog, so she has tiny Maltese. As the Brittanies suit me, so the Maltese suit her. Her current dog is really nasty (bites, etc) to everyone except her, but generally the Maltese are OK – tiny and prissy looking, but still just dogs.
Just for fun, here’s a pic of my master, Maggie, pointing a songbird along our lane, my younger dog, Chase honoring Maggie’s point as he does in the field; and my wife’s little dog, Lilly, pretending she is also a huntin’ dawg by honoring Chase’s back of Maggie. They stood like that - frozen dead still - for several minutes until I gave the release command. Too funny.