14 or 15?

Not too savvy on the 6.7L. I bought my 6.0 new in Oct of 06 and am now thinking about another new one. What would be the advantage of waiting to order a 15? Are there any really good incentives to buy a 14? I don't necessarily have to have the latest and greatest, especially if I save a few thou. If there isn't much diff. in price, I'll probably hold out for the latest and greatest.

Thanks in advance,