There is no question the 9mm is a plenty capable round (and my personal favorite) buy there is also no question that the 40sw has a significant boost in power. If your talking 'need' then there is no reason to look at the 40 but if your rounding out your collection, then the 40 is a must have. I'm looking for one myself. Not sure but I may be leaning towards the new Magnum Research one. The Cougar and the M&P are also high on the list.
597 VTR, because there's so many cans and so little time!