NOTE: I actually run 95% of my external audio on a couple of old 1394a
drives. For most things, including Ardour up to so many tracks, they
work fine. If you buy the right 1394b drive case it will support 1394a
interfaces also so you can use it with the built in connector for now
and go to 1394b later if desired.
There is nothing wrong with 1394a, 1394b or AFAIK eSATA for doing
audio on an external drive. They will all work and work fine. If I was
going to buy a new controller to do this stuff I'd go with 1394b.
Thomas would go with eSATA. IT's all cool.