Is RAID-0 faster with 7200 rpm SATA II or 10k rpm SATA?

I am purchasing a new high-end workstation that needs to be as fast as possible for multi-tasking – mainly Office app’s (Outlook, Word, Excel…) & Internet research (many open windows). I am planning RAID-0 with two 7200 rpm SATA II drives OR two 10000 rpm SATA drives, but I don’t know which will type will be fastest. Machine spec’s: Processesor is Pentium-D 930 (3.0Ghz, 2 x 2MB L2, 800mhz); RAM is 2G of 667mhz ECC DDR2 SDRAM; product is Dell Precision 380; HD options: 80G 10k rpm SATA w/8MB or 160G 7200 rpm NCQ SATA II w/8MB.