magus, channeling a shocking grasp crits. The group is using a crit deck. Does the magus just get the weapon crit on the card, or should they get the weapon and the spell crit, since both would normally deal double damage?
Since the deck is an optional thing and not really a rule, this might get better answers in the Advice section of the forums. (You can hit the 'flag' button at the top of your post to request the thread be moved, if you like)
That said, the crit cards are really pretty good, so I would let the magus choose. If he chooses to use both for crits, then both will also apply to fumbles. This can be devastating (and hilarious).
As a GM, I would let the player pick one of the two possible effects to apply. Both seems too powerful. Of course, the reverse is also true, if a NPC magus gets a crit, I get to pick the better effect.