Nah, purely tabletop gives Morathi the advantage. The Circlet of Iron is a magical item, so doesn't count for Malekith's own skill and it also provides extra power (because the die you roll can contribute to a miscast) while Morathi's First Sorceress special rule is purely about her own skill and also effectively acts as a higher Wizard level.
I'd say he's a step below in most of his skills tbh though. Like, yeah, he's a master swordsman, but he's not as good as Tyrion, he's a mage, but not as good as Teclis, a general not as skilled as Settra, etc. etc. He's very scary, sure. Ultimately, whether he's scarier than Morathi (who, depending on your preferred edition, has been a Chaos Cultist for millennia without screwing up that relationship or getting fucked over by Chaos) depends on how you're confronting them.
Considering the Circlet is welded into his skull, I feel like the difference is mostly academic.
And the tabletop rule writers often don't bother to make a separate rule giving characters a bonus to casting if they've also got an item that does that, for simplicity's sake. Like, if we exclude item bonuses Teclis is only a Level 4 wizard with no bonuses too, he just knows extra spells.
And yeah, he's not literally the greatest warrior or the greatest mage or the greatest general. But he's also not that far off from the top in any category, while also massively outclassing them in others. He's not quite the best mage on the planet, but he's a far better warrior than any of the other contenders. He's not on the highest tier of weapon skill, but he's got much better magic than any the guys above him. And so on.
Like, the fact that Tyrion, who is probably the greatest swordsman alive, is a better warrior than him is not some kind of knock against him. If we were to go by tabletop stats again, the only characters with higher Weapon Skill than him are Tyrion, Ungrim, Archaon, Kouran Darkhand, Valkia, Shadowblade, Skulltaker as well as Keepers of Secrets and Bloodthirsters.
He might not be quite as good at magic as Teclis or Morathi, but he's also not that far below them and solidly the third greatest elven wizard alive.
We don't actually know he uses Battle Magic consistently. It's not like he goes to war all that often actually, so it's entirely possible he doesn't.
Even ignoring the novels, considering that in the armybooks Malekith is quite casually tossing out spells that banish waves of Daemonettes and destroy a Keeper of Secrets, and that he's described as equal if not superior to Teclis who then went on to turn the tide of the battle of the Finuval Plain by smashing hundreds of dark elf warriors with each spell, I feel like it's a pretty tall order to claim he can't consistently cast Battle Magic as the Empire refers to it.