Since the Liquid Metal Armor is a Metac, it requires internal energy to deploy and more internal energy to maintain. This makes it cheaper in terms of upfront cost, but it is very expensive in terms of energy usage.
On the other hand, an exoskeleton or mech is a permanent artifact. This makes them more expensive to buy, but it means that one won't need internal energy to deploy and use them. But their advantages don't end there.
Both exoskeleton and combat armor enhance the power of their wielder. This is something that the Liquid Metal Metac can't do.
The Liquid Metal Metac will create a weapon for the user. Then the user will have to bear the burden of using that weapon.
So if the user is not strong enough, the artifact created by the Liquid Metal Metac will be a useless burden. But that is not the case for the exoskeleton armor or the combat armor.
