Motorcycle tire traction is generally sufficient so that lean angle limits are the determining factor in most cases - the pegs start scraping and if you try to lean even more, the rear wheel levers up off the road. Not good.

But rider dynamics also play a part. If I slide up to the tank, slouch over to the side, getting as far forward and low as I can, the motorcycle will have a much lower center of gravity and reduced lean angle required for the speed I'm carrying.

Same thing works on a bike. But I don't see the pros "hanging off" much. Perhaps that's due to the skittish nature of the bike since it has much less stability at speed due to a much smaller rotating mass (wheels and tires).

In the end, I see a bike losing traction well before a motorcycle. Still comes down to the ratio of contact patch-to-rider/vehicle mass.