Hi there, so if you have Windfoil/wingfoil experience, then you probably do not need the biggest boards anyway. Depending on your weight, I would rather go for smaller models.
But for teaching/learning, the Lift foil plus those 2 models are the best we have yes. To the q's:
Learning/lift, a hardboard with similar width/volume, will mostly always lift earlier due to with the sharper rails and stiffer board shape.
Durability the Sky Air will almost always be better for smaller impacts, scratches etc. The composite board will handle bigger impacts with sharp objects better.
More volume is mostly linked to thickness or width, width = stability. Sky Air/SUP's are mostly limited to a max of 15cm anyway.
Both boards are fun, the composite board will always feel more "performance" oriented, as it is stiffer and has more defined rails. But for beginners, the Sky Air is a great option too.