User blog comment:ChipTheMonk/AD Malzahar./@comment-94.134.194.253-20120726152649/@comment-1663379-20120726185647

Play him as Ad caster when you already have Ap mage mid, from sight of Ad caster, he got very good ad scaling, 1.0 for each Voidling(And they can attack very fast) and you can summon 2-3 of them at the same time, just try to calculate how much damage you will get from building Ad compare to other Ad caster.

Both Ap and Ad Malzahar have very good scaling, you can play him either way, but make sure you tell your team so that your team comp won't get ruined.