Terry, Bill,
There are some major differences between the PB9 and P5 w/P5T. ( I have not bought either yet but have done a lot of investigating as I plan on purchasing soon)
The PB9 replaced the 2K2 but only has 4 trigger inputs instead of the 6 the 2k2 had. It also has a battery to allow sounds to be played when using variable voltage track power and voltage is low or shutoff so you will get shutdown sounds. There have been serious issues with the PB9 and the battery charging circuit. You should check with Phoenix after purchasing one to make sure it has the newest firmware ans software. They can check via the serial number.
The P5 is mainly for DCC and has two chuff trigger inputs which can be reprogramed. The P5T adds motor inputs for speed sensing and 6 trigger inputs for sounds. No back up battery. Works well with constant DC power like constant track power or battery power. Best thing is it is about $20 cheaper.
The only reason I can see for buying the PB9 is if you are using variable voltage track power and want shutdown sounds when you power off or reverse direction.
If you want the max sound triggers and are using constant DC power save the $20 and go with the P5/P5T.
Just to clarify, are you using the Revolution TE or one of the older TEs?