Not sure if this applies. My '44 A's rear wheel position has much more range than our 730's has. I can go from row crop width to wide by moving only the wheels on the axil, while we have to take the fenders off the 730 for row position, move its wheels on the rims and so on to get that much difference. It's a pain in the neck, so we end up never using it in rows but leave it wide for hay making. I don't know if all the number series are like that or not.
Like has been said, the A will be lighter. For hay making and a lot of other work (seeding, spreading fertilizer, etc) light is better. I want mine as light as possible so I don't rut up my hayfields in first cutting. I can float right over wet areas with my mower on the A where the 4040 and the discbine would rut it up.