Why not have both?

Anyway... In my opinion pick Wizardry 8 if you want:

- in depth character customization
- cerebral, in depth combat
- constant sense of danger

Might and Magic (4-7, at least) is good for:

- character customization that is not overly complicated but still varied enough
- fun dungeon romps
- decimating hordes of enemies
- tons of loot, gold and experience