well, either HQ with that setup would cost the same, so it really depends on the type of army you play. If you have an assault army, then a DP can be great, good in combat and even if he gets shot at (as he can't hide in a unit) he's taking the heat off your other units.
On the other hand, Tzeentch armies tend to be more shooty, if this is the case, then a sorc. is the best option, hide him in a unit and use his powers when the enemy gets close.
always go wings (or bike if you take a sorc.), the added manouverabilty comes in very handy, even if the rest of your army doesn't move that fast.