Wahoo,
Axle weights are serious changes and since the geometry of the coach has not changed there is a definite value in having greater capacity. This is especially true as coaches got slides which added weight,
But usually changes that affect ride comfort are not so critical. Those subtle changes may have produced better ride quality but may not be discernable from coaches with and without the changes except to engineers who are using instrumentation to measure the revisions. I cannot tell you my IFS coach rides or handles any different than the two solid axle coaches produced previously for example.
Bottom line is ride feel is not likely to have much value unless you are highly trained as a test driver and you have experience with both types, pre and post changes. But increasing the weight rating of an axle is very important unless you prefer to never weigh your axles, or use those weights to select the correct inflation pressures for your coach tires based on axle position.