Depends on the trappings. Armor created by an Air spell might deflect attacks so they miss, Water might absorb the attack, and an enchanted Jacket could also...which fits the situation and block used best?
It seems based on the information I've gleaned in this thread so far that (upon GM's discretion) a character could create a magic shield as a reactionary, defensive action (which would be a good idea if they have a rubbish athletics skill) and then create magic armor too during their own turn.
This would effectively stop any attack that does not meet the shifts of the shield, but if it does, the character would roll athletics or some other kind of block (like with a weapon) to stop/evade the attack, and if it gets through, the magic armor would also take shifts off of the attack before actually chipping away stress, right?
That actually sounds pretty reasonable. It seems like a character who is madly trying to stay alive could layer the magical defenses in that way.
That said, magic armor is not all that great except for not weighing a character down and some evocation focuses (like spirit) are good at deflecting almost everything.
Using "Aftermath" as an example, Murphy has armor that I would rate a 3 against projectiles and a 3 against melee.
It seems that body armor would be just as good (if not better) than magic armor and is always in effect.