AbdulAlhazred
Legend
Here I must disagree. With damage-at-start from the sphere the enemy takes the damage and then has (almost) no decision to make. Sure, he can move away, but that won't stop the wizard from damaging him again. So the choice is not between "stay in my preferred position and be damaged" or "move away and avoid that damage". The choice is more like between "stay in my preferred position and be damaged" or "go somewhere else and take the same damage". Hardly a choice.
I disagree. In the start of turn case the wizard could simply say "Hmmm, I don't want the monster to move to location X" and threaten THAT location with his sphere, so he has JUST as much control in each situation. In fact its almost a trivial difference. The only real distinguishing feature between the two cases is with s-o-t damage the wizard's team can force move opponents into the zone and guarantee they will take damage, in the e-o-t case the opponents can use forced movement or other techniques to save their allies from taking damage. I would say the difference is very marginal but favors s-o-t effects as providing slightly more reliable control. E-o-t effects are better for leaders where the effect is beneficial to their allies and the ally gets a chance to move in and benefit right away vs waiting until the start of its next turn. Thus what you see is controller zone-type effects tend to trigger at s-o-t and leader buffing effects tend to trigger at e-o-t.