I've used both and using vectors for the position and velocity of both the ball and the wall is very much easier for modelling collisions at arbitrary angles in

I've used both and using vectors for the position and velocity of both the ball and the wall is very much easier for modelling collisions at arbitrary angles in both 2D and 3D. Working out the new angle and magnitude of a ball bouncing off a wall at an arbitrary angle is a nightmare in comparison. Using vectors and vector math also works well when modelling more complex collisions (i.e. solving the problem of balls flying through walls at high velocity) and other physical phenomenon like friction and gravity.