I'm not convinced that either is ideal.
If you were going to use this for track saw work and repeatedly putting kerfs into the surface, the ply would eventually splinter away from the top layer; laminated MDF - presumably melamine or similar - will leave unpleasantly sharp edges and potentially dull the blade more quickly. And a melamine surface would be more slippery than I'd want.
But, hey, depends very much on your planned use!
I'm using Valchromat.