You don't "win" collisions. If you fly into another players plane, you take damage. If you don't, you don't take damage. If another player flies his plane into you, he takes damage. If he doesn't, he doesn't take damage.
If you didn't ram, and took damage, you were shot. There is no ramming without taking damage, and there is no taking damage from being rammed.
If anyone knows more about the collision model code than HT, I urge you to step forward and set him straight. Otherwise, this is how it works, and I suggest you accept it, even if you don't understand it.