Maybe the cost of the Naiant PFAs went up, they used to cost significantly less than a pair of DAD6001. The aren't larger, mine are almost exactly the same size, but in actual use they are significantly more compact. I'll explain-
The DAD6001 has the advantage of having a female microdot connector input, so a stock, standard male microdot-terminated 4060 will attach to it directly. But that's also a disadvantage, in that the microdot connector is at the end of the adapter opposite the XLR output, and when plugged directly into the input of the recorder the adapter leaves the rather delicate microdot connection and mic cable sticking out vulnerably. The microdot connection and mic cable strain-relief require around an additional 2" of well-protected clearance. That problem can be remedied by using a short 1' long XLR-RA patch cable between the recorder input and adapter, so the adapter is no longer rigidly mounted to the recorder.
The Naiant PFA has it's input on a short cable. For stereo use, typically a pair of PFAs are wired to a single stereo input connector (usually mini-jack or mini-XLR). I've made a slight cut in the rubber strain reliefs of each of my PFAs which serves to form a protected side cable entry. The cable turns 90 degrees before it exits the strain relief and nests into the cut. When the PFA is plugged directly into the recorder, the end of the rubber strain relief then acts as a rubber bumper against the inside of the recording bag, rather than the thin mic cable and delicate microdot connection getting crushed. The disadvantage is that the non-microdot input connection either requires re-termination of the mic cables, or requires female-microdot>mini-jack or mini-XLR adapters.
One additional detail to note. Jon can build the PFA to be either signal polarity inverting or non-inverting. His standard for low voltage mics is inverting, which corrects the typically inverted polarity output of most small electret microphones. The DPA miniature microphones produce a non-inverted output signal, so if you go the PFA route, ask for them to be non-inverting. The DAD6001 is non-inverting as it was designed to work with DPA mics. The signal polarity issue is probably only an issue if you are mixing multi-channel sources. You can always invert polarity of the track in your editor of course, but this avoids the need to do that, and allows for internal mixing in multichannel recorders which do not provide signal polarity switching.