R407C was invented to match R-22 pressure, temperature, enthalpy etc. properties and works well in systems designed originally for using R-22. R-410A was developed and systems were designed specifically for it to take advangtage of its unique thermodynamic properties. Whatever you do , your best results will be if you use a refrigerant in a system that was designed for it. R407C and R410A will both be around for a long time. R-22 is being phased out, but will still be available for a while and cost in future is unknown.