A or J. Really don’t think it matters. That character denotes the motor, not battery.
Also bear in mind that they can tweak the voltages in these motors to get the performance they want.
I appear to have the larger battery, and have timed 0-60s at the original 5.3sec. I have a J vin, which people have tried to say mine should be the “slow” one as that’s not the old motor used in the Performance model.