Sata and pata refer to the connection type
Pata uses a 40 way parallell connector (although generally a 80 way ribbon cable is used)
Sata is the serial version of the ATA protocol
and is a newer (and faster) form of ATA
typically max transfer rates are
pata=100Mb/s
Sata1=150Mb/s
Sata2=300Mb/s
(although none of them actually achieve anywhere near the max)
sata is the new king .... even scsi will probably be repaced by a sata type interface shortly.
The one big disadvantage is that the connectors are a little flimsy and have a maddening tendency to fall out (sataII is better)
although a good quality cable and a little care will overcome this.
If you have a newer box ... or intend to build
go sata
We just switched one of our clients from ATA to SATA for their server, and the thing flies in comparison to how it performed before. Most modern motherboards have both ATA and SATA controllers on board, but you can get plug in adaptors for older boards (Adaptec do one, for example).
When SATA was first introduced there were problems on some machines if a SATA drive was used as a boot device.