Thanks to the example song that comes with PT 11, which is well mixed and just needs a pump for mastering, I was able to compare the behavior of my dynamics processors and, very specially Sonnox Dynamics and Limiter against several IK Multimedia dynamics processors and their Brickwall Limiter.
IK Multimedia compressors for Master Bus
I've tested every IK Multimedia compressor in Master Bus, including Fairchild 670, White and British Channels, Precission Compressor / Limiter and Classic Compressor.
Without any doubt the Classic Compressor delivers the most musical sound in that bus, with just a touch of color and a nice punch. The Opto works nice but lacks that kind of warmth that the Classic Compressor has.
As Limiter, just the Brickwall Limiter does the job.
Comparing IKM vs Sonnox
I can make the Sonnox plugin to sound quite close to the Classic Compressor, if I set up the Warm section to 50% more or less.
The oposite isn't possible, since the IKM one is always coloring, you cannot achieve an uncolored result, for this you should use the Opto Compressor, that works awesome also.
But, without coloring the mix, the Sonnox Compressor works better, in my opinion.
In IKM Classic Compressor to achieve a more clear mix in low end, the Side Chain Filter should be pushed up to 78 Hz more or less to achieve same results than with Sonnox Dynamics, which always sounds clearer, even without using the EQ section.
Giving the same compression ratio, controls settings for each plugin clearly differ and, you have to find the spot that better works for each one, often even forgetting how controls were named.
Visually, Sonnox plugin is more intuitive but, sonically I love that Classic Compressor.
Maybe where there is less discussion is around the Limiter.
While you can get a more accurate control over the IKM one (more range of attack / release ranges), the protection level of the Sonnox is higher and, the Dithering button is really great to check if the mix is going to sound bad once transported to a 16 bits environment.
Compared to those plugins, I find Blue Cat Audio's plugings more complex to control and, sonically slightly behind those. But, I still love their Meter Pro plugin. What a nice one!.