Thank you for your answers. In my mind, the sorcerer doesn't have access to the spells I like to cast such as: restoration, prayer, aid etc. Most important arcane buffs are already taken over by the summoner of our group.
The Mystic Theurge has a very slow spell progression if I would go for Oracle/Sorcerer.
I want to play the oracle like a Holy/Smiter Priest (e.g. Wold of Warcraft) but the option in pathfinder are limited for a divine spontaneous caster without armor. I want to keep the divine spell list, get access to some arcane spells and be armorless based at the background story of my character.
I'm not sure how to balance the lack of armor with any other benefit. Another idea could be an additional arcane spell per level known, but would this be too strong?