Wizards cannot choose magic armour unless they have an option for 'normal' armour. Magic is the stuff of dreams and nebulous imagination, and rests uneasily alongside the physical. There is little more real and physical than wrought metal, and its tenacious actuality casts a peculiar and unyielding shadow in a Wizard's mind. As a result, most Wizards cannot wield the Winds of Magic if they wear armour of any kind - their magical senses are smothered by the armour's embrace – and so cannot choose an item of Magic Armour.
The only exception to this is when a Wizard has armour as part of their standard equipment or an option for 'normal' armour, such as light armour, or a shield. Such sorcerers have trained their mind to focus and can wear armour without confusion or penalty. The chief examples of this kind of Wizard are the dread Chaos Sorcerers of the frozen north.