Hi Johnnymac
I have an 08 SMB rb50 with the pop top. Note that you can only get the pop top on the RB (144") model so that eliminates the concern of whether LB or not (but perhaps a longer model could sleep 4 efficiently tho?). Note that the 50 model comes with a bench/couch with 3 belts... but, the kids would be out of striking distance! (
just kiddin!)
It is only my girlfriend and I in ours but i have witnessed several friends with small children (1 or 2) and occasionally a dog "manage" weekend trips in a Westy. All I can say, it is rather obvious the SMB RB50 is more space friendly then the Westy. I think 4
adults could easily camp in the SMB poptop but there would have to be some dancing going on to avoid a lot of collisions, and if it were bad weather out or more then a few days, it could get wearisome. BTW, all our friends' kids love
our poptop.
The Sprinters are great handling vehicles and are surprisingly easy to maneuver and park (I do try to park "strategically" tho - ie leave myself some space) and have tons of space to carry things. no wonder they are such a popular delivery vehicles - DOH! Mine is getting 20mpg. So as a 2nd vehicle that you can camp out of, hard for me to imagine something better (unless you need 4wd, but note that there is good clearance for some "easy" offroading - look for another topic already posted on this subject).
As to limitations in campgrounds, State parks etc., I have found the the RB model (which is ~19') fits in most places where I have seen limitations signs. I am pretty sure I could park in tent sites and get away with it... until someone complains when I turn on the Espar water heater! On a recent trip to Zion NP, we were able to drive thru the restricted tunnel without an escort whereas most bigger RV could not. But the checkin lady at the Zion campground entrance noticed the electrical hookup on the side of the van and so she "forced" us to camp with the big boys. I think it will just come down to where, when, and who you are dealing with and how good a sweet talker you are... but perhaps someone else knows the "rules" better (especially out in CA).
hope that helps...