The G22 magazine has a slightly sharper angle between the floorplate and the mag body, to match the difference in the base of the frame cuts between the G22 and G23. If you press the bottom of a G22 frame against a tabletop, the barrel and slide are parallel to the tabletop; if you do the same with a G23, the barrel and slide will point at a slight upward angle.
Otherwise (as said above), the G23 mag should hold (and have counter holes on the back of the mag body for) 13 rounds of ammunition. The G22 mag holds 15.
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)