Pick one that will suit your needs and a floor plan that you can live with.
My recommendations or suggestions would be try to get one on a
Chevy Chassis They will give you a better ride and more room among other perks.
The Mercedes as stated already costs a lot more and their service may be hard to come by in many parts of the country.
The Chevy or Ford have a larger network of dealers and service centers.
As for levelers that is a personal preference,they do add some weight to the chassis and with a larger RV that extra 150 to 200 lbs may be handy for more cargo,I've done quite well without them for the last 26 years.