If you absolutely have to have an external drive, the Plextor is better. I have one at work and it does a reasonable job. Use Firewire though, it's a lot more stable compared to USB 2.0, with lower CPU usage .
If you can buy an internal drive, do. There are a lot more choices available, including ones that write better than the Plextor. I got the Plextor at work because it's attached to a laptop.