Your onboard controller supports both SATA and Ultra ATA natively, and the only big difference you'd notice is that SATA drives are hot pluggable (with "Safely Remove Hardware" icon in Windows).
Your integrated SATA controller would be ideal for a removable SATA drive, I have a 2.5" notebook drive mounted in a removable cage expressly for that purpose. My Vantec EZ-Swap EX supports both SATA and USB 2.0, so I can use it as a high-performance backup drive in my PC and as a moderate-performance transfer drive with other systems.
But beyond that feature you won't notice any major differences. I wouldn't put any money into Ultra ATA right now as I tend to carry over drives from one build to the next and Ultra ATA is dead.