How does an Airbus pilot decide whether to use HDG-V/S or TRK/FPA guidance?
It's mostly up to points 2 and 3 on your list rather than personal preference:
Note that most ATC instructions (beit on departure,cruise or initial approach) will ask of you to fly a specific heading and/or a specific climb rate (v/s). This makes the hdg/vs mode the 'standard' mode to be used durring flight. This is also the mode where the F/Ds provide an easy to use guidance for the pilots to follow.
The reason for this Hdg preference for ATC is beyond the scope of this question, and is quite a nice narative on how historically we arrived at using heading for separation, but I will say this much: imagine ATC software attempting to interpolate the track of two converging a/c , to determine minimum separation and/or collision conflicts. Now imagine there is (unkown to the atc) changing wind along route, and both a/c will change hdg to maintain proper ground track. The math required is mind-blowingly complicated...(because changing hdg will change time of arrival at intersection,etc )
Anyway, once you look at some final approaches you will see that there is usually a final approach Track and a (3deg usually) glide path angle posted on the chart. The reason is that being closer to the runway, you start to become a bit more interested in your path wrt to ground rather that wrt to other trafic.
TLDR
TRK-FPA, as part of normal operating procedures, is only used when flying the final part of a non-precision approach, and is usually engaged  about 1 NM before the FAF.
Mind you, it's use is not prohibited outside of that, just there is kinda little use for it.