Exchange 2010: Windows Disk/Volume Layout Question

I used the Exchange 2010 Mailbox Server Role Requirements calculator and for the databases, it recommended 16 drives in a RAID 10 configuration.  For a 4 database design, which of the below approaches do you recommend?

1)  Present all 16 drives to Windows as a single basic disk and create multiple partitions/volumes over the single basic disk (1 partition/volume per database).  In this situation, all the IOPs are shared among all the databases.

2)  Break up the 16 drives into 4 RAID 10 groups and present 4 basic disks to Windows (1 Windows basic disk/volume per database). This would result in dedicated IOPs for each database.

Thanks.