1st Gen Mazdaspeed3 Front lower control arms, OEM vs Aftermarket?

Looking at the 2008 Mazda parts fiche, there are two different part numbers for each (i.e., left and right) front lower control arm even though they are visually the same during a casual inspection. There is one part number for the MS3 and a different one for the non-turbo Mazda 3's. Aftermarket units like those from Delphi or ACDelco show the same part number for both models for each side. I suspect the OEM units have different bushing stiffnesses, but without having fresh examples side by side, I can't say for sure. I have two questions:

1) Does anybody know the difference between the two OEM lower control arm part numbers?

2) For those that have tried Delphi, ACDelco, MEVOTECH, etc. units (not the "economy" units), did you notice any difference between the OEM MS3 unit and the replacement that made for a worse driving experience? I understand that this is likely not quite an apples-to-apples comparison because if you are replacing a control arm and are comparing them, you would likely be comparing the new replacement with an "old" unit.

Thanks in advance for your help.
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One more point as this certainly factors into it: My MS3 is modded and puts out 310-315 HP at the wheels, so it would be nice to hear from those with modded cars.