The game is well-balanced, and thus no character class is "better" than another. Furthermore, the racial benefits-- which consist of four additional attribute points-- are pretty insignificant given that you gain three attribute points per level. There are also quests and books that will raise your attributes even further.
That said, I've found it better to "main" as a mage, primarily because magic tends to be pretty strategic. The AI can't handle the full range of spells, and using the right spells (as opposed to using the right talents) can often be the difference between victory and defeat on the harder battles. This doesn't mean that mages are "better" characters, just that they require more careful management than the AI can deliver.