kinell, Eper lists 5 different rear caliper assemblies for ph1, in some cases some of the constituant parts (bracket/cylinder/etc) match between v6 and ts.
PH2/3 is a bit simpler, the same assembly for TS/JTS and one for the V6s (3.0 and 3.2) though, this was obviously far too simple and so there seems to be one TS variation that has the same as the V6s...
In theory Aluminium parts will be lighter, so reducing unsprung weight (weight attached to the wheel side of the springs)
ETA: ok,, comparing cylinder and bracket part nums:
PH1 V6 : one set matches the PH2/PH3 V6 Parts, one set matches one of the PH1 TS sets
PH1 TS : one set is unique, one set matches one of the PH1 V6s set, one set has the same bracket as the PH1 V6 but different cylinder
PH2/3 TS/JTS : unique
PH2/3 V6 : matches one set of PH1 V6s
Alfa Romeo, keeping you on your toes since 1910