A Saradomin sword is better xp per hour then d scimmy and rune defender, but the down side is if you get a task like basilisks which require a mirror shield a Saradomin swor wouldn't do much good. Even if you kept full guthans it wouldn't help on those task either. My suggestion is to sell guthans go to aviansies till you have enough money to have a seconday weapon like a scimmy, might only take like one short run. Overall get d scimmy and SS, well if you want to spend money.