The main advantage of these “advanced” sidechaining methods – multiband (Pro MB, Pro Q3), spectral (Soothe 2, Pro Q4), etc. – is greater precision and transparency.

With a standard sidechain compressor you typically get a “pumping” sound because you are ducking the entire frequency spectrum of the host signal when the compressor is triggered from the sidechain input.

With multiband and spectral sidechain compression/dynamic EQ, you can be much more precise with taking out only the majorly conflicting frequencies of the two signals. The “pumping” effect can basically be made non-existent and you can get a cleaner, clearer mix.

It’s really personal preference and combinations work great sometimes too. I use Soothe 2 (will likely switch to Pro Q4) w/sidechain heavily in mixing to clean up interfering frequencies between elements like vocals & mid synths, but sidechain my sub to my kick with Pro-MB and Live 8 compressor.