The Schloss Rules:
1. Only digitize once. Do not re-digitize.
2. Use the best A/D that you have available.
This could be either the DAT or Digi001 or whatever. I often prefer DAT, because then I have a "for-free" archive of the original material that is off-line, and much less likely to disappear, especially after a few years. But there is another reason to use the DAT (if you are doing an acoustic recording using microphones): the electrical and acoustical environment of other A/D's (especially the one in your sound card) is likely not optimal. Why? Because it's inside your computer (electrical noise), and worse, it's inside or next to your horribly noisy computer with fans and hard drives spinning. You can turn all this stuff off when you record to DAT, or you can move to a silent room with no computers at all. Note that the digital transfer you do later from DAT to Digi001 (or other interface) is not subject to any of these problems.
3. Do not resample unless you have to.
This usually means recording at 44.1. If you have access to very high sampling rates, you can record at 96kHz or higher, get a higher-quality recording, and then downsample when you're finished. In this case it's worth it.
3a. Don't use MP3 files as source material for mixes or other forms of sound manipulation.
Note: You can set Sync Mode to either INTERNAL, or to S/PDIF from Setup>Hardware menu. Either one should work. Note that if you set it to S/PDIF and the DAT machine is on, it will take the sampling rate from the DAT, which may be wrong! If you're not actively using any other device in your setup, set Sync Mode to INTERNAL.