height/size and ski touring

I don’t have any size insights, but my understanding is that AeT and AnT are unique to an individual and shifts in those #s for that person are relative to their fitness. So not applicable to compare across to yourself as an indicator of theoretical fitness equivalency.

I think your’re going to have to look at deeper training history (last 5-10yrs), recent training history (last 6 months), immediate history (last few days of training or illness), technique etc for differences in the apparent fitness.

For example, if I did a muscular endurance workout 1 or 2 days ago, and am in a higher volume week or block, I will not have the same performance as an equivalently fit friend who just had a lighter rest week. As another example, I have 30yrs of ski history and my up and down technique and my thermoregulation is way smoother than someone who is a yr or 2 into the sport. Similarly, if I am coming down with or recovering from a cold, my performance tanks.

Are you on a heavier class of skis and boots? I’ve sure found my aging body appreciates the lighter gear.

Tim,
I am pretty tall as well and my wife is smaller and shorter than your wife.
From my experience smaller, lighter people tend to slow down much more from heavy packs than bigger guys. Even though this seems to be more of an issue in ski mountaineering where packs are generally heavier.
However, I wouldn’t underestimate the importance of technique and efficiency, also on the uphill. You can “waste” a lot of energy trying to balance out bad kickturns, lifting your skis up by an inches with every step etc. This can really drain even fit guys very quickly.
You mentioned that this is only your second season, so I would probably start looking there.

1.7kg weight difference per foot is quite a lot as well.

physics is a factor. moving more mass over the same terrain requires more calories.
Power(watts), work(joules, kinetic energy), mass, velocity, etc are all part of physics.

one calorie can produce something like four units of work(joule). you are more than 2x the mass of your wife, and therefore you are doing far more work(measured in joules) than your wife to move your mass over the same terrain. in simple terms, you need to consume far more calories than your wife to support your efforts over the same terrain.
if you are taking in calories suitable to your mass, and your wife is still outperforming you on climbs, her sustained power/weight ratio(FTP, etc) is higher than yours.

my explanation here is not perfect, and physiology is very complicated and unique to each person, but if nothing else, you need to eat alot more than your wife.

“We both have avi bags, so she is carrying a lot more weight for her size than me on her back, but she can get away with a lighter setup skis/bindings/boots than me.”
How different are your boot-binding-ski setups? If she’s in an entirely different class of gear weight than you, then that can make a huge difference.
As for the optimal body size for skimo, one of the fastest racers out East is such a tall strong guy that he qualifies for Clydesdale in running races (even though he of course is anything but fat).