There are really other factors this is dependent on.
Is the SELLER doing high volume trades as it is that falls under the eye of Jagex? Is their IP in a problem area like China and your's in another country? As for gold risk to the straight phat I would assume the Phat is safer in terms of bans. But is that best when putting so much money on the line with a high scam potential vs buying gold in bulk with money you can walk away from if lost?