Well, all three of them, magic - stealth - combat based custom classes. Just play the game with three different characters
They are all fun...
Or maybe choose the one you prefer then level up enough to make your char good in all three gaming styles...
Anyway Morrowind is a hack'n'slash favoring game - there is no trouble your katana cannot get you out of... magic is useful for any char, but really not absolutely needed - enchanted items you will find will compensate.
Playing a mage as a first char can be difficult - things start to be tough when the bad guys close in and you are low level and unarmored...