The quantity that can differ between the two gases is the mass of each gas.
Given that the gases are held at the same pressure, volume, and temperature, they will have the same number of moles according to the Ideal Gas Law (PV=nRT). Since the molar volume (volume per mole) would also be the same, the gas constant does not vary for different gases in general, but is specifically a universal constant when referring to the Ideal Gas Law. However, the mass can differ because the gases may have different molar masses.