opinion on disk speed

I have a choice to make on a RAID enclosure:

14x 36GB 15kRPM ultra 320 SCSI drives

OR

12x 72GB 10kRPM ultra 320 SCSI drives

both would be configured into RAID 10 over two SCSI channels using a
megaraid 320-2x card.

My goal is speed.  Either would provide more disk space than I would
need over the next two years.

The database does a good number of write transactions, and a decent
number of sequential scans over the whole DB (about 60GB including
indexes) for large reports.

My only concern is the 10kRPM vs 15kRPM.  The advantage of the 10k
disks is that it would come from the same vendor as the systems to
which it will be connected, making procurement easier.