More entropy: Atom or Macromolecule?
Ahh entropy. The bane of many undergraduates. You won't need a lot of mathematical rigor needed to solve for absolute entropies in most biological fields so it's best to think of it abstractly. 

Consider the atom. What can it do? Well if you remember from chemistry class, it can bounce around a process we call translate, and the electrons can basically switch spins. For the most part, if you had a single atom alone in the universe, that's all it could do. Move around and have its electrons switch states. It's best to think of these as "states" of the atom.

Let's see, the atom can move in the X direction and be in spin up. It can move in the x and y direction and be spin down...etc. But the point is, there is not a whole lot the single atom all by it's lonesome can do. 

On the other hand, if we start adding other atoms to the mix, say across chemical bonds, then they can start to do more. If two atoms are bonded, they can stretch and contract (vibrational states), they can rotate around each other, and they can do everything the atom can do as well. 

As you can see, there a lot more "things" or "states" that the two atoms can be defined in at any one time. They can be rotating one direction, vibrating in one way, moving in another... etc etc...even this sentence seems to be getting more chaotic! And that is really all entropy is. Adding up more and more ways for matter to get into all these possible configurations. 

So the answer to your question is the macromolecule. It has tons of atoms and bonds. An uncountable number of ways to rotate, translate and vibrate, and be struck with photons, and emit light, and do all kinds of chaotic "stuff" (you can count it actually, it's just really hard).