This is more or less my take on it also. Hopkins would probably improve more due to not having as good an amateur career as Jones but he was also older and would soon start to decline physically, so I don't think there's any dramatic difference. Hopkins should have received the decision in the first Mercado fight imo. It was naturally a much tougher fight for him at that altitude also. There's a reason that Ecuador's national football team often beats Brazil, Argentina and the likes when playing in Quito. The altitude is a killer for anyone not used to it.
The only reason Pavlik picked up the title in the first place was because Hopkins had already slipped.