"nickelman".....There is something else you should consider. When washer/dryers first regularly started showing up in RV's, they were the combo units. The first of those were not vented and took a long time to do small loads of clothing. When the idea caught on, they started making taller cabinets and installing the stackable units.
When someone tells you they didn't like theirs and it did small loads, they're probably talking about the first generation of all in one units.
Our last coach, 2005 Monaco Diplomat, had space for the all in one unit. I had no interest in adding one of those. When we bought our new coach, we definitely wanted a stackable unit. They work great. We can do a weeks worth of clothing in two loads. We often go camping with our two adult daughters who both have RV's and the washer/dryer has come in handy when the grandkids have an accident.