One thing that does need to be point out COP is not the most important factor when installing one of these type of systems.
Run time is the most important factor.
It can be difficult to match heating and cooling loads, as many clients tend to need more of one than the other. What is required for equipment selection are a group of "load" profiles,
you may find it is better to run machine at 90% high efficiency and 10% low effriciency, than try to have a machine that runs 100% at an intermidiate efficiency.