First of all, there are two 'versions' of P25 - Phase 1 and Phase 2.
Phase 1 is 12.5 khz wide, single-talk-patch-per-channel, just like 12.5 khz narrowband analog, and it uses the IMBE vocoder (very old).
Phase 2 is TDMA, just like MOTOTRBO, which gives two 'virtual' channels in one 12.5 khz channel, and it uses the AMBE+2 vocoder, just like MOTOTRBO.
P25 Phase 2 is a vast improvement over P25 Phase 1, in my opinion.
I think that the 'advantages' of one over the other are going to depend somewhat upon the application. Although the AMBE+2 vocoder is definitely a lot better than the old IMBE vocoder.
John Rayfield, Jr. CETma
Wow, really sparked some debate with this. Anyway, what's the advantage of MotoTRBO over P25? Is it the AMBE vs IMBE Vocoder thing?