Range and my logic is this,
with range you could be killing different types of monsters fairly easily dispatching them with ease due to the fact that many monsters can be ranged easily. There's a lot of monsters to choose from that would be perfect for this, such as Blue Dragons, Hellhounds, Aviansies, Yaks, Black Dragons. And it's a good way to make money too, by killing blue Dragons, Hellhounds, and even Black Demons(mostly focusing on the Rune chain drops, and clue scrolls). It is also fairly cheap to level if you were to focus on getting fast exp, perfect example would be Yaks or Rock Crabs, even using it against Green Dragons, also Aviansies. With 13m worth of knives-that's saying you pay for 1gp per exp which would not be the case, but with 13m worth of knives(iron or steel) you would get 99 range.
As for Mage, you would be bored. The current best way to train it and not lose as much money is Hi-alching. Which other than being still fairly expensive, is rather boring.