Which would provide better battery life? I'm interested in the theory, but more interested in practice. Let's assume a Mid 2010 MBP 13" 2.66 GHz. 8 GB RAM with: 250GB 2.5" Hitachi Travelstar 5K500.B 5400RPM SATA 9.5mm Notebook Drive 8MB Cache Versus 2 x 120GB Mercury Extreme Pro SSD 2.5" Serial-ATA 9.5mm Solid State Drive. (RAID 0 via Disk Utilities) Mixed workloads of Mail, PowerPoint, Excel, Acrobat, Camino, etc.