Wave cancellation is a bad indicator in the same way that ABX is a bad way of testing whether there's a difference between £5000 a metre speaker cables and the regular variety, or double blinded placebo controlled tests are a bad way of checking whether a homeopathic preparation is more effective than tapwater. We're into the realm of audiophile voodoo.
If two waves cancel, they are the same. If two waves cancel to less than about -110dB then they will sound the same unless you crank it up until you're in physical pain. So if a waves plugin and an appropriately set up other plugin produce sounds which when rendered to wave files cancel to less than -110dB, then those wave files will sound identical. And unless somethings wrong with your rendering, this is because the plugins sound identical.
Certainly there are differences in sound between Waves and other plugins, but when the plugins are producing different sounds, the waves won't cancel.
I'm talking about the Waves SSL 4000 plugins vs. the $500,000 SSL 4000 analogue console.
In all the wave cancellation tests you might notice that nothing ever reaches absolute cancellation. They reach down to a certain number of negative dB, but don't absolutely cancel. That's because there are different. The waves plugins only acheive -35dB cancellation and that is a lot.
Eric Persing on wave cancellation:
"I'm all for tests and empirical data, etc, but IMHO, we are nowhere near the ability to
measure such differences in sound quality with something as simple as a
phase reversal test. The best tools we have today, are still very one dimensional.....I'm sure it
will get better and better in the future. I remember having this same old argument with my
high-school electronics teacher, who said that since our measurements of the sawtooth
wave of the Moog and the Arp sawtooth looked the same on our cheap oscilloscope, there was
obviously no difference in the sound! (Sounds pretty silly now right...well, at the timethat was the best measurement we had). "Empirical" data will always only tell part of the story"