i work at Dell in server product development. I think it is important to inject a little realism into HP's claims about BL 260c being 64% more power efficient than other blades (specifically the PowerEdge M600). If you look into HP's disclosure, you will find that that number is based on comparing :
a BL260c with dual E5450 processors (3Ghz Harpertown, 12MB cache) running with an obscure power mode called "static low power" which basically turns it into a low voltage part, 8GB of memory (in a 2 x 4GB configuration), 1 SATA drive without a RAID controller
an M600 with dual E5345 processors (2.33Ghz Clovertown, 6MB cache) running at full power, 4GB of memory (in a 4 x 1GB configuration), 2 SAS drives + RAID controller.
So not only are these products not in the same class from a feature set standpoint (enterprise class vs. low featured SMB focused), but the creative license used to compare two products configured with vastly different features is amazing. If BL260c is so great in terms of energy efficiency, why didnt HP even try to compare apples to apples features?
if you want to see a true apples to apples, independent 3rd party evaluation of Dell vs. HP blades see http://www.dell.com/downloads/global/products/pedge/en/pe_blades_specjbb2005.pdf