You need to check if the 1 TB drive is just two 500 gb drives put together. If that's so, then you need to consider reliability. I use 500 gb drives almost as disposable drives. I like to mirror my drives for backup/archival purposes, and I prefer two separate 500 gb drives than a single 1 TB drive.
As far as seek time, burst, buffer etc, unless you're editing digital video (especially HD), it shouldn't really matter. Most available drives are sufficient for digital audio.