The main disadvantage of HFO blends
Is the higher refrigerant cost from R1234yf or R1243ze. For Co2, it is both efficiency and cost from ultra high pressure and transcritical operation. For HC greater than 150g charge like in Unitary A/C application, it's A3 high flammability will likely require a secondary loop and will impact cost as well as efficiency due to added pump and secondary HX loses.