[Al Skierkiewicz]

jpsaul7usa,
What you have run into is the variation of production and your own design. If you are absolutely sure both motors are running exactly the same direction then the problem has to be something else and here is the list.
1. There is more grease in the transmission and therefore more drag. Some teams clean the trans and repack with better grease.
2. The speed controllers are not calibrated, so calibrate following the procedure in the data sheet.
3. You have more wire in the path to the slower motor (or a poor crimp) and therefore more resistance in series with the motor/speed controller/breaker panel. Make wire lengths the same or at least as short as possible for high current systems.
4. The thumbwheels on your joysticks are not centered or the joysticks are not tracking.
If you cannot isolate any of the above then you may have to compensate in software.
5. Practice, practice, practice!
Finding a bad crimp could be hard but may show up as a hot connector. We solder all crimps that feed high current devices and all connectors on #6 wire. Even if you loop two breaker panels together with #6 you are still adding resistance that limits the current.
Let us know what you find.