whether I use Magic or Physical power is dependant upon my foes.

Missions...

Gilbert:
Paladin/Blue Mage
Double Sword (Nagrarok, Sequence)
Peytral
Ninja Tabi

I just send him on his own. If the enemy is any sort of a threat (Which isn't very often at all) I use Angel Whisper and Mighty Guard, if not I mindlessly attack everything until I win.

Vs. Undead...

Eldena:
Red Mage/Summoner

There is no better way to defeat undead than Doublecast Phoenix.

Vs. a friend in two player battles...

Alot like me, my friends love to play FFTA, we set up Tournements from time to time, In this situation I use a Viera Red Mage/White Mage. For player Vs player duals Red Mage/White Mage cannot be beaten if used correctly. If anyone can come up with a scenario where my Red Mage/White Mage can be beaten by another class I'll be very impressed.

Because of the Red mage/White Mage combination Physical power can never be as good as magic, but I love the ol' Double Sword Paladin that I find myself using way more often.

Conclusion
Useful: Magic
Favorate: Physical