The problem is more likely that the actuators are responding differently to the same input; if this is the case, putting both of them on the same controller wouldn't help. If you really need the two actuators to move in sync, there are two basic solutions:
- Hardware. Create a linkage such that the two actuators must always be at the same locations. This would not necessarily need to be as robust as if you were trying to drive things with just one actuator, but it must be good enough to equalize the differences.
- Feedback sensors. Whether encoders or string potentiometers, put a sensor on each actuator and adjust the speeds to each so that they move together.