Also I think osim/sem is more common among native Serbian speakers in communication on a daily basis. Izuzev is more sophisticated word, but both have the same meaning. Hope this helps, too :)

Difficult to explain. The both have almost the same meaning. I will give you the explanation from our dictionary: IZUZEV: (Verbal adv.used as) 1. prep. ith gen. except. Ex.: Svi su došli izuzev Nade, (Everyone came except Nada/ 2. adv. Razgovarao sam sa svima izuzev sa Milicom, (I have spoken with everyone except (with)Milica). OSIM/SEM: 1.prep.with gen.except (for), but. Ex.:Svi su došli osim/sem Olge, ( Everybody came except Olga. 2. (as a part of a conj.) Doći ću sem/osim ako se razbolim. ( I will come unless I get sick). Osim/sem što su napravili nekoliko grešaka., ( Except that they made a few mistakes). Good luck!