Although CCC is a buying tool when considering any RV. The buyer has to be aware of certain things. First and foremost most times the number is not always completely accurate.
From there the numbers get even more confusing.
Most manufacturers don't weigh individual RVs as they leave the assembly line. So the CCC listed, can be way off. Factory installed options e.g. double door fridge, tile floors, roof racks & ladders, are often not deducted from the CCC of a particular unit.
You also have to read each sheet carefully to see what is included in the calculation. Some allow 145 lbs. in the calculation for the driver only , where others allow 145 lbs. for each seat equipped with a seat belt. Others include the weight of a full tank of water, in the coaches weight before the CCC is calculated.
The base model of my coach listed a 5,000 lbs. CCC in the brochure , the sheet, in the coach lists CCC as 3,785 lbs. 1,215 lbs of factory options.
Newmar, at that time weighed each coach and produced an individual sheet for every unit.
Still some room for error as dealer could add options too.
The sales brochures for my coach has 2 pages dedicated to option weights, right down to a listing of one pound for the C/B radio , " prep package."
If CCC is a big concern , and you think you may be close to being over weight, loaded. Take the coach out and weigh it before you buy.
There have been other posts , where on factory orders; Tiffin, buyers have specified a higher GVWR chassis , to improve their unit's CCC.
The other differences ; in units of the same length; can come down to the quality of the build, materials used etc.
JMHO. I'd trust the accuracy of , Tiffin's , CCC listing , over some of the other manufacturers you listed.