The gear ratio will affect the acceleration of the output shaft on the motor. If you are talking about the acceleration of the back shaft on the motor, there might still be differences between motors with different gearboxes due to the differences in friction. We do not have a datasheet or specifications for the acceleration of those for those gearmotors. Is there a particular reason you need to know the acceleration?
I need to understand what is the time to reach fully speed for a very timed and quickly paced application. I could just read out the encoder positions and do a little bit of math to find out the acceleration but I was hoping their might be a datasheet on these motors.