Don't buy the weight at all. It depends on how it is supported and how it sits against the side of your head. Some could wear Pro-4 AAs all day, I could stand them for less than half an hour, yet I can wear heavy ear muffs in my shop all day. My Senhiesters were not comfortable, but my Yamaha YH-1s are only after I modified the head strap.
The test set can give us relative measures of distortion and energy storage. It can give us "suitability" as far as amplifier compatibility and what it takes to reach some fixed threshold, like 100 dB maybe. Max SPL does not matter as most are capable of permanent damage to your hearing. I really don't care if one set gives 110 dB and the next 120. If more interest would be it there was some safety limit and how it behaved.
No, cans are one product you really need to try on. Consistent testing can narrow the field and that would be a very great service. Well, people do buy shoes online. Maybe I am outside 3 standard deviations.