
Horses for courses and all that these plugins could be awful for different purposes and tastes. If I'm in a hurry, I go for the Class A, as I find it is easy to make subtle improvements but quite hard to make them worse! I rarely do any mastering without either the Class A or Aquamarine, depending on the character of the mix already in play. ago FWIW, after buying Mastering Compressor for 70, in the license page I have a special offer to buy Class A for 99.99, so you could have both Mastering Compressor and class A for a total of 170 today. Even if it is also made by Brainworx, though, it could be somewhat different in character and in the parameter responses, especially if it has been made with less eye to efficiency, or with user-controlled oversampling options. Save your pennies and buy Class A for 129.99 during Black Friday sale. The character is less ideal for me but I would say that it is still a better plugin overall (plus you get a powerful bass and treble EQ plugin with it). This is even better but it is much punchier and can even be set to pump.

I also have the Acustica Audio version, Aquamarine. Certainly, the Class A with which I'm familiar, is not very suited to surgical problem solving for mastering or in other contexts.

These are mastering compressors and work well on a complete mix as part of a larger chain to impart character and make subtle alterations to the dynamics. I haven't used PA's Shadow Hills Mastering Compressor (the green one) enough to judge it. I love the PA Shadow Hills Mastering Compressor Class A.
