In the end, SCH is a little stronger at single-target heals, and WHM is stronger at area-effect heals.

Other than that, there aren't too many differences, so play what you like. Scholar might do a little more single-target damage, while WHMs likely do more AE damage with Holy. Scholars have an easier time regaining mana, but that same mana regen is used at the expense of some of our best heals (Lustrate). As you've noticed, WHM gets sleep and SCH does not, so WHM is superior for crowd control. WHM also gets better looking gear and you'll unlock a unicorn.

I enjoy the added challenge of controlling the pet and my character at the same time, so I like Scholar more. However, there will be times when your group takes big AE damage as a Scholar and you will be desperately wishing you were a WHM. Medica/Medica II are hugely powerful tools that SCH really can't touch, as our AE heal is quite measly in comparison and needs to be used before and after a big area effect attack.