Microstepping actually don't improve accuracy much at all. It's biggest benefit is that resonance is less likely to occur in your system. Resonance is when your motors vibrate and lose steps or stop turning altogether at certain speeds.
I'm not familiar with with your drive, but some use techniques (besides microstepping) to deal with resonance. Your system also might not have any problems. Since you already have the drives, it's certainly worth giving them a try.