You shouldnt have any problem speed matching two Athearn genesis locomotives, esp if you equip them with the same type of decoder. The motors are virtually identical. I'm assuming you're getting the new sd70m, but even if your not the only major difference in the older releases and the newer ones is the light board and/or sound decoder.
Im looking into getting an athearn genesis sd70m and an athearn genesis sd70ace sometime this summer, just wondering if the motor in these are similar to each other and if I would have to speed match them or not since they arent the same model.
Thanks
Greg