42RH / A500 question

IIRC, they are different gear ratios;
The smaller one is 2.74-1.54-1.00
to the larger ones 2.45-1.45-1.00
That difference is 11.8%, a lil better than from 3.55 to 3.91 allowing you to run that much more or less rear gear, and/or, a lil less/more stall, to optimize for your application.