People talk about this as if it's not a matter of preference... maybe it's cause they can't think of a way to ensure both levers are at the same height without their bottoms being level with the bottom of the drops...?

I say put your levers wherever you want them on the bars; experiment with different angles for bars and levers to see what suits you. When you've nailed it down and want to ensure both levers are at the same height, pull your stem off and put the bars on a flat surface, then move one of the levers until all four points (ends of the bars, bottoms of the levers) are on the same plane.

And I have NFI why people insist on pointing the levers straight ahead; I find them far more ergonomic when pointed in slightly. This also protects them a little from crash damage.