Best in class

The examples you mention relate directly to the van itself and not the upfitting. The ERA is a Sprinter thus the answer is much the same be it Roadtrek, Pleasureway, Airstream, Advanced RV and others that upfit the Sprinter. Versus Ford, Chevy or Ram Promaster, I think it is a matter of service availability driving most opinions. I don't know if anyone has any solid facts as to "best in terms of reliability, lower cost to maintain and service, resale value, comfort and ease to drive." Those are opinions and people get comfortable with what they own.

I drive a Sprinter simply because on balance that van design meets my personal needs and criteria better than the others. Sometimes I curse diesel when some gas engine a-hole is hogging the only diesel pump at a service station out of a dozen gas pumps available. ;)