Just a couple of comments here… Not that I’m a weightlifter or anything but if you want to be “fair”, don’t compare heights. Compare your dress shirt sleeve length and your chest measurement. A 5’8" guy can have longer arms and reach than a 6’0" dude… People are built differently.
The two measurements above are the ones that will impact how much you have to lift the bar for a rep. The other measurement that of course comes into play is the width of your grip on the bar.
This is something you can do something about, to an extent. The first two are pretty much set unless your name is Mister Fantastic :lol
When you’re lying on the bench, the bench doesn’t care how long your legs are. Being more or less coordinated doesn’t matter either. What matters is lifting the bar up off the rack, down to your chest, then up to full lockout, that’s it.
Energy required is proportional to the height difference from touching your chest to the top of full lockout.
After measuring all the dimensions and stuff, I think in most cases, where you have a height difference of a few inches, you can compensate by changing grip to make things more “equal”.
At the end of the day, you are probably talking a relatively small (5% to 15%) difference in required energy to perform a rep for 90% of the general population’s physiology, and accounting for how they play into dimensions of the linkage made when one is at “full lockout”.
The ability to adjust a bit in grip width also comes into play here.