I use usb-serial cables for software development all day every day and I pretty much refuse to use the ones with the Prolific chipset. It has too many issues, and can bust the usb protocol stack in the pc which requires rebooting to repair. Other issues are very slow code downloads and more.
The FTDI chipset seems to work like a charm. The cables using this chipset are little harder to find in the US but I did a quick google and came up with this.