Yesterday I flew a 2:1 aspect ratio delta and a 4.5:1 AR wing in the same wind on the slope. Both were electric powered. The 2:1 plane was stopped in mid-air, with power on, by the increased wind where the slope lip changes to horizontal... the wing had no trouble getting thru.
The delta also had very poor penetration in the wind away from the slope.
Basically the difference was the induced drag of the low AR plane being higher than a better AR configuration.