Not sure if there is a correlation between XP and Gold with the difficulty of the house gladiator that you get pitted against. But right now it seems the higher XP choice is usually pretty close to the high gold count also.
Maybe a more strategic choice could enhance this part of the game.
Perhaps high XP but low gold and a low XP would yield a high gold payment.

Just an idea for those that may want to retard their fighter in XP but garner as much gold as possible, which would benefit the freebie player but also slow thier XP speed while being able to possibly purchase better armor or weapons.

A high XP low gold really wouldn't damage the pay player since they probably already have multiple fighters and have a higher earning potential with an assortment of armor and weapons already. But does increase their XP and level advancement quicker.

Just a thought.