I know a Watt is a Watt. However, you use fewer Watts when a datacenter is ran on 208V Therefore, you can generally pack your racks to 75% of capacity, rather than just half (Improving datacenter density).
Plus it runs cooler, so lower cooling bills.
http://www.apcmedia.com/salestools/S...NQZ7_R2_EN.pdf
I've been involved in a couple of data center designs