The whole HVAC market has changed in recent years. There has been a shift from looking only at heat output to looking at efficiency. It is still vital that enough heat is produced to meet our needs, but it means when we compare heat pumps we have a slightly more complex task.
First of all we need to remember that heat pumps are designed for different jobs. There are swimming pool heat pumps that are quite different to home heating devices. These will be rated for a size of pool and then by efficiency.
There is no standard test for efficiency for a pool heat pump. Often, but by no means always the test is done for raising the pool temperature to 80 degrees Fahrenheit when the outside air temperature is also 80. Check, though, because heat pump efficiency is very sensitive to environmental conditions (it is, after all, how heat pumps work).
The well known brands like trane heat pumps, carrier heat pumps, or goodman heat pumps (plus many others that you will know) have good web sites that give you plenty of information to compare the pumps. What is most important however is that you purchase something that meets you needs - inefficient use of heat pumps is when you buy something that is too big or too small for the job it is aiming to do.