The main difference between the Taurus G3C and G2C magazines is the capacity:
G3C: The G3C comes standard with three 12-round magazines, but 15- and 17-round magazines are also available.
G2C: The G2C magazine holds 12 rounds.
The G3C and G2C are functionally identical and use the same magazines, including Sig 226 and Canik magazines. Aftermarket magazines will also fit both.

Hi Matthew, The G3c and G2c magazines are interchangeable.
Stay safe & have a great day!

Hi Matthew and welcome. The magazine body is identical. The floor plate on the G3C grip and magazine has a slight cutout for better magazine removal compared to the G2C magazine floor plate. The magazines are 100% interchangeable between the G3C and G2C. G3C on the right in this video: youtube.com/watch?v=PqUUPf8UBkQ