I tried to be very specific about what I meant - the "grip" I'm talking about is braking and steering grip only. No question AWD gives you better traction for acceleration. But I'd love to hear your take on how AWD improves braking and steering at highway speeds.
If you guys are mashing the accelerator on snow-covered highways then...
As for World Rally Cross, that's a much different type of driving. They drift through every corner so 4x4 is better for them. Are you doing that on the highway?
Here's the rationale for what I'm talking about:
https://www.engineeringtoolbox.com/friction-coefficients-d_778.html
If you let your front wheels spin freely, they are more likely to be in static friction since the engine isn't trying to break them free. Think of it this way - in any turn, you have the sideways force on the tire trying to break it free, plus any powered wheel ALSO has engine torque trying to break it free. Unpowered wheels will almost always stick to the road longer than powered wheels. So unless you're rally driving on the Trans Canada to Lake Louise 2WD has a better chance of keeping you on the road.
To the best of my knowledge nobody has ever tested this. Lots of tests about accelerating and braking, none about turning at highway speeds. Please let me know if I'm mistaken.
EDIT: What do you know, found supporting articles right after posting:
https://www.popularmechanics.com/cars/a3091/the-myth-of-the-all-powerful-all-wheel-drive-15202862/
https://www.wheels.ca/news/does-all-wheel-drive-actually-help-in-winter-driving/