Opinion of an Aerospace Engineer and long time KingCat owner/pilot.

For a given angle of attack, raising the ailerons will decrease the wings lift and increase its drag. Any time you turn the air it takes energy and that is drag. So if you fly the same angle of attack with crow as with out you have a higher sink rate and more drag that you can compensate with either more power or a steeper descent. For most of us this makes it a bit easier to pick your landing spot.

Raising the ailerons also increases the effective washout on the wing with makes the model more tip stall resilient, which decreases the possibility of a departure.

Raising the ailerons reduces the maximum lift the wing can generate, that is just the effect of negative camber. Since the wing is making less lift the stall speed is increased and the approach speed should be higher also. This allows the control surfaces (all of them) to generate more control authority to deal with upsets due to gusts or pilot mistakes. The KingCat can land so slow that it can get into trouble in gusty conditions, crow helps this a lot; many other models are the same. However crow really only helps out on lightly loaded models, which is why it is of no use on full-scale aircraft. The manufactures of airliners are trying to improve the L/D in landing configuration so they can use less power and make less noise on approach. On a clean, lightly loaded model we would like a lower L/D so it does not float as much.

You can decrease the flaps and get some of the benefits, but that also decreases the drag, so you shallow out the approach and find it harder to pick your spot, and you decrease the effective washout which increases the chance of a tip stall.

Steven