If the same motor runs slower on both ESCs then the problem, if that's the right word, is the motor and not the ESCs. These are not exactly the highest quality motors made (with all due respect to MFA). The armatures are possibly hand-wound on converted treadle sewing machines by Chinese outworkers for ten cents apiece. As such the number and even the thickness of the windings will vary quite a lot - QC not being trendy in the ROC - and this will create variations in back-EMF. This is the reverse voltage generated when a motor is switched on and off, which is the way modern speed controllers work. The more back-EMF there is then the slower the motor will run. In contrast, if you have two ESCs of the same make and type then the likelihood of significant variations on their outputs is very low.
Moral? Change the motors, not the ESCs.
Suit yourself.
DM