Two main advantages to my A-1 Alum 2 pc converter is lighter= less rotating weight, and easy to change stall/ flash by just changing the stator, can be done at the track.
Also keep in mind you can then sell all your steel 1 pc converters, to help cover the extra cost. I had 4 steel converters in our trailer, now just a couple of stators. One converter for alitude [ Salt Lake City @ 4400', 7600' DA], another one for our Hemi, actually two, another one for bad weather [ hot, humid] and another to try a looser converter.
I just called A-1 to get the stator that came close to my main steel converter, I did find the Alum 2 pc was a bit tighter than my steel one using the same part #.
Depending on how many converters you own, and how much changes you want try.
I can see how Bruce is not interested in Alum 2 pc when he only races 7.0 Pro, and doesn't want to go faster/ quicker.
Jon