Answering the question is simple as long as you clear up one issue...

What's more important, the length of the reign, or who was more dominant at the weight?

If it's all about the former, then the answer has to be Calzaghe. If it's the latter, then the answer has to be Jones, because the prime Jones would smoke the prime Calzaghe and Jones' win over Toney is more impressive than any win Calzaghe had at 168.