Nealhood: do you mean the AN DAC KIT 1.1? The AN is more expensive than Scott's DAC, it comes in a large, heavy metal housing, it accepts both SPDIF (on BNC) and AES/EBU (on XLR) at the flick of a switch. Scott's is less expensive, much smaller (2.5 inches square pcb) and accepts SPDIF, but you can also add AES/EBU if you want. Technologically, both Scott Nixon DacKit and AN 1.1 are non-OS, both use the ever-popular CS 8412 as receiver, but whereas Scott Nixon's DacKit uses TDA1543, 16-bit DAC chip, AN uses AD 1865 18-bit ladder DAC. Both passively convert current to output voltage via resistors, but the AN follows this with a CRC filter, using a ferrite-core inductor, and then a common cathode triode stage, delivering extra gain. Scott's DACKIT does not have CRC filter, but he has info about a simple RCR filter for de-emphasis if you need it, and offers a tube buffered version of his DACkit with 6DJ8/6922 in cathode follower mode, with lower output impedance. Output coupling in AN is 0.47uF, whereas with Scott Nixon's DAC it is 100uF. Both have high output impedances, which require some care in system matching, but Scott Nixon's TubeDac and SaruDac+ now offer sinc filters, which offers better system matching flexibility.
Voltage regulation in AN is provided via three discrete regulators, built with op amps, and pass transistors, and referenced from LEDs, whereas Scott Nixon's DAC simply uses two LM78xx-type regs. Whereas AN offers upgrade paths from their basic entry-levels, Scott Nixon has dropped some of the kit options. AN offers an upgrade from Beyschlag metal film resistors to their house-brand tantalum resistors, simultaneous with an upgrade from WIMA MKP/Elna Starget caps to Black Gate/Elna Cerafine for the bypasses. Moreover, AN SIG versions uses output transformer for AC coupling. Scott Nixon uses Black Gate with Oscon or Panasonic FC caps standard. In addition, I just noticed he is offering a 4A transformer for the TubeDAC and added power supply upgrades for his dacs, which makes good sense. It is best to visit Scott Nixon's site, since he has made some additions, and there are even more options than I have mentioned. If you are an experienced builder with proper solder station, get the DACkit, otherwise buy a fully-assembled/tested board as sub-assembly or in the housing.