If nothing else with sleeping bags there is an EN rating that allows cross brand comparison, bag fit notwithstanding...
However I cannot see how a backpack comfort rating could be determined mechanically, so you need to know
each bran's take on that.
For me my two ULA packs are accurately rated, however a couple of Osprey were a bit optimistic.
At the other end a certain frameless pack was far overrated. What was meant to be the its normal carrying capability
felt like torture for me.
I believe that it is a bit like with wine or beer, what one thinks is "good" can only be based on what one is used too.
Franco