Recommended device class for Primary storage pool

This might be like asking which motor oil is the best to use, but I'll ask anyway. I am looking for recommendations for the configuration of primary storage pools. Do I go with DISK or FILE, and what is a good volume size to use?

Currently running TSM v5 and v6 servers on Windows and right now all of my servers are running with DISK. I did try setting up a couple v6 servers to use a FILE device class on their primary pool, but there was problems with the servers leaving a lot of "volumes" after a migration;i.e., not deleting the dynamically created files. This bothered me so I converted them back to DISK.

Now, I have a storage system with a lot of free space on SATA disks. Am thinking about moving my primary pools off of my high-dollar FC storage and putting it on these SATA disks. Thinking this might be a good place to put sequential volumes as opposed to using it for random/DISK-based I/O.

Seem to recall reading somewhere that sequential/FILE was the way to go for the primary pools. Cannot seem to find that article now, so I am asking the experts here what they use and why. Your recommendations and configurations are eagerly anticipated...