I think a lot depends on your level of investment in the character and the value of a Jack Sparrow figure in your collection.
For folks like Gipetto0812, Rzeznikk and myself, our Jack Sparrow figures hold a great value to us personally and we've invested a lot of ourselves into making the "perfect" Jack for our collections.
I had the DX06 and heavily customized it, but unfortunately had to sell it. By the time I could buy it again, DX15 was being released so I went with the cheaper, more updated figure.
As far as stock figures go, I actually consider the DX06 the overall better figure, I think the materials were overall better. However, the size of heads and hands on DX06 are a little off, hands a tad too large, heads a tad too small. DX15 resolved both with smaller hands and larger heads, but the trade off was less variety of hands and the hands are specific to Pirates 5 with extra wraps and finger tattoos. I bought DX06 hands for my custom. Despite the size issue, the variety and look suit me more.
These latest Jacks look to have small upgrades. The hand variety looks great, but again, you're getting ones specific to a single movie that don't represent any other in the series.
If you're on a budget and better served saving money for totally new figures, I think staying with the DX06 is just fine. A compromise could be keeping that figure and trying to buy a piece or two sold loose to upgrade it. Depending on how much you want to upgrade though, you'd be better off buying an entire figure because the prices on parts can run high.
with no wheel to save some money - I already have a wheel from the DX06
