Roger, with T powering (also known as parallel or A/B powering) any noise in the DC supply will directly add to the signal, so with that system an extremely well-filtered supply is essential. Also, if you power several microphones from a single DC supply, the audio must also be decoupled from the supply separately for each microphone or you will get crosstalk between channels.
Phantom powering has neither of these problems. I think it's fair to call phantom powering a fundamentally better system, technically, than parallel powering is, as long as you are connecting your microphones to balanced inputs.
--best regards