I have race kites 19 edge and 11 velocity that are the best at staying in the air. With a foil, any kite will have no problem to go upwind.
I think downwind is the problem that needs more attention especially for newbies.
Now for light wind this problem is greater as it would be nice to have a lightwind mid to low aspect kite that is produce lighter to stay in the air like race kites. Are we talking about strutless kites here? or is there something better?
Generally, for hydrofoiling, lighter kites is better in all sizes IMO, no doubt at all and no downsides.
If you also use your (smaller) kites for riding waves, or for freestyle/jumping - it would not be good with light kites, and better to use the ones you have.
But for the big size, light kites is way better yes.
This is not particulary for going dowind, but also for handling when not up riding.
Why do you want a medium or low AR kite ???
As such a kite will not generate nearly the same power in marginal conditions when you want to get "up", nor for downwind.
But if you use the big kite for other things than hydrofoiling, it makes sense.
And maybe it is more "pleasant" regarding turning, so better for the freerider although the low end is not quite as good, yep.
How do you ride downwind ?
For freeride (racers must tell me how they do), I either go deep downwind with high speed and kite parked, so the apparent wind is "pleasant", good power and high speed, but you dont get overpowered as you go as deep as possible without losing speed - this is easy and really comfortable.
Or, I loop the kite around, typically 1 or two times forward, and then one or two times the other way - and continue like this.
Especially with a bit longer lines, you can go REALLY fast and really deep now, much deeper than if riding with the kite steady - a bit more attention is needed, but fun.
Some also work the kite in sinus I think, but I have not found any advantages doing this, only for riding halfwind or upwind in the lulls of course.
If you ride downwind with the kite steady, a light kite has no advantages really, but if you turn and loop it around, a lighter kite will work much better on the upstroke, especially if you ride too much towards it of course
You might have a point, that strutless kites can be lighter, but they are unfortunately not as high AR.
But even when missing this, the lower AR might make them better at turning with slack lines, so you can use the extra agility that the high AR ones dont have, eventhough they have much better power spike
What do you weigh ?