I would replace both yes.
I've rebuilt individual calipers sometime apart on the Ae111 and found that after one was done, clearly that one was more efficient than the other. Only became really annoying when braking heavily, the car would pull to the side with the better brake (o/s/f). That and in the wet the good one would reach lock up quicker than the other.
I know most people don't drive a car really hard all the time, and as such would propbably never know anything may be off, but in a sh1t or bust situation I'd rather know the brakes worked evenly rather than potentially altering my course (dependant on road condition) into oncoming traffic etc.
I'd certainly thouroughly check the other side to be sure and at least get a quick brake test on a brake meter to prove its up to scratch.
Edit - If the pads and discs are in serviceable, safe condition I would reuse them.
It would be a good time to replace the brake fluid too, if its last replacement date is unkown or longer than two years. Water in it is the most likely root cause for the corrosion that may be causing the piston to stick in the first place.