My point TOm, is ALL the numbers have the be looked at. One can not just use GVWR for instance. Nor is it per say the most important.....but probably really close to the top. 
What is legal per say, vs legal per the rv net wt police, will be different also. 
max gvw is probably the one that is important. BenK gcwr less loaded TV, is baloney, because as I pointed out, if you are at max gvw, you do not have hw, which his stance is the hw is included in the gvwr. That is not a good way to look at it either, as some may not understand the hw needs to be included in the gvw.
Now you are still down to a, one needs to use ALL the numbers available to them. 
Only the light duty trucks, ie under DOT class 3 or typicaly one tons have a gvwr that is less than the sum of the axel wt totals. So to a degree, axel wt ratings can be just as important as gvwr, if not more so! one can be under gvwr, but over an axel wt rating, and potentially be more unsafe than one over gvwr by a 100 or so lbs, but under the axel wt ratings. 
Then the typical GCWR is typically nothing more than an axel ratio difference. How is towing with a 3.42 gear set at say 15K, rated for 14K, less safe than a rig with 3.73 gear sets, rated to 16K? Reality, assuming everything else about the rig is the same, there is no difference is overall safety towing. 
Too many ifs ands or buts as to which number is more important per say.
marty