Definitely money, lets say you had 2B cash and 3B in items/99's banked. you ould have 99 herb, mage, prayer, firemaking, fletching, con, etc. banked. many of thoes dont take long to get to 99. definitely cash>xp.
another way to put it.
lets say you had 200M xp in cooking or 200M cash. what the fuck could you do with 200M cooking xp that is different from 13.143M xp, nothing. just seems to me that having lots of xp in one skill or to have it divided out just doesnt cut it when a lot of cash is involved.