Not sure why this is even a debate? The guys at a.t. will tell you phantom power is key..period. Not that other methods wont "work"...they just are not ideal. The mic mod and 3 wire bb are simply a much less expensive alternative. You will get better performance with phantom vs. the other couple options.period.
It is a debate because there is a good bit of missinformation here. Speaking of A.T., they will not tell you phantom is key, "period." I have spoke at length with them about the 4.7k mod and the 3 wire powering through a 9v battery box. They are aware of these mods and understand that they work perfectly for our purposes. You must understand that the AT853 series was not designed for our purposes. If you ask a AT tech about phantom power for the 853's he might suggest phantom is important. This is because they are assuming that you are using these mics for the purpose they were designed for. Installation. In in installation setting the mics must be driven with a ballanced line, as there are often long cable runs. I think Richard explained this well so i wont continue. Bottom line is a ballanced, phantom powered source is just not nessesary to power any electret microphone in short distance applications.
As far as your claim that the mod/3 wire solution is much cheaper solution, I don't see how you get that. A 3-wire battery box is about the same cost as a pair of phantom adapters...
I had one hell of an expensive 2-wire AT setup not long ago (at853(4.7k)->CA9100->ModSBM-1->iRiver), costs the same as my three wire setup now (ATu873r->Oade PMD660).
The three wire solution is cheaper *in parts*. It costs only about $20-30 to make a battery box, either two or three wire. It costs even less to add a 4.7k mod and to use a regular two wire battery box. Then there is the added advantage that you can plug directly into a regular recorder (minidisc, Edirol R09). The problem, is that unless you're a hacker, you can't find a 3-wire battery box easily. A few of us (Chris Church, Busman, and myself) made battery boxes for others, but we charged for labour as well, so that drives the cost up.
Yes, if you've got phantom power already, then by all means use the adapters. That is probably the *simplest* solution, since you can just plug directly into the recorder without extra connections/worries of a battery box.
To each is own, it depends what you've already got and where you're going.
Richard