There are a couple of models of DAT decks around, and as long as there is a A/D converter in front of it, they make very little difference. All decks write down the same 1's and 0's from the converter, unless there is no converter, then the deck does make a difference. SCMS is the only other difference. Serial Copy Management System was put in place to prohibit DATs from being copied hundreds of times over and over again. In fact a master (original copy) is only allowed to be copied (cloned) once. That is unles SCMS is defeated. Most models of DAT decks on the market defeat SCMS so it is for the most part a non-issue. Here's a list of the commonly used decks today.

HHb: The HHb PDR-1000 Portadat is the Cadillac of DAT decks. No ifs ands or buts about it. It's more equipped in a portable than most of the home models by all brands. I don't know off hand it's A/D conversion specs, I believe 20 bit, but don't hold me on that. I know it's better than the D8 or M1 for sure though. This model defeats SCMS on the masters it produces.

Sony: There are a coupld of portable Sony models on the market right now. The D7 and D8 are essentially the same, except the D7 can not master on 44.1kHz (if it is doing the A/D conversion, though it can still make 44.1kHz tapes if it is receiving 44.1kHz data from a digital source). The other 2 models that are very similar are the M1 and D100. There are 2 major differences. Their voltage signal is different making the M1 difficult to deal with, at times, when actually taping a show, and the D7 and D8 do not defeat SCMS. All 4 of these decks has an 8-bit A/D conversion.

Tascam: The Tascam portable deck is the DA-P1. The only other common "full sized" portable besides the HHb. This deck falls well above the Sonys, though still below the HHb in terms of ability. It does defeat SCMS, and it's A/D conversion is, either 12 or 16 bit. I believe it is 16-bit though.

Hopefully this helped you out somewhat. If you find this confusing have any suggestions for me to clarify, e-mail me