Which would you choose?

[DGDobrev]

I would reset till I get ancient amulet and banner of true faith or ancient amulet + prismatic helm. In my eyes, that's the best start for a mage.

The dragon slayer is nice, but it is an item with morale and it may become useless very early in the game, and you can't suppress it easily.

The price of the items is not a problem, even on impossible. If you clean up darion properly, you will have enough money to buy troops, both items and even more. In my impossible paladin game, I reset till I started off with gladiator sword and ancient amulet (both giving runes) and a marshal's baton found on the cemetery zombie. It took quite some time, but that was one of the best starts possible.