The difference is that they are reverse of each other. (see picture.) The retaining screw is usually on the other corner(s) of the peg, which can mean you would have to re-drill to mount them securely. Also, if you were to turn the tuner knob in one direction, the tuning posts will turn in the opposite direction for left vs. right tuners.
They should be perfectly functional, but you might be happier with the results if you hold out for the correct type of tuner to match what you are replacing.