I would choose tech. Cuz i never choose magic in any rpg and i think tech is better in Arcanum. That is , of course, my oppinion.
Since you brought about other RPG games, is this the first game about technology and magick combined?
Return to krondor is first rpg that has magic and tech for one character. Mixing spell items and using equipment.
I'm gonna choose tech way. Basis? I want to be a diplomat/fighter/inventor character. Besides sine I played BG I don't choose mage class for my main character.