Since the theoretical CoP is not a function of the gas, only of the input and output temperatures, there's no way you can gain net energy by using different gases in the heat pump and the heat engine. However, in a practical device how close you can come to the theoretical figure does depend on how efficiently you can move heat energy around the system. This is easier when you use the latent heat of vaporization and condensation to move heat energy from place to place. Thus the CoP attainable in practice is a function of where in the temperature and pressure range a gas liquifies. An ideal gas system, although just as efficient in theory, would be less efficient in practice.
People use different gases to match the properties of the gas to the application.
For example, a compressed gas won't liquify if the condenser is hotter than its critical temperature. On the other hand, a gas with a low boiling point will generate too high a pressure if used in a heat engine. And so on. The different CoP figures in your tables probably refer to different temperature ranges. From the calculation you do it looks as if the CoPs quoted are the theoretical ones.