Middleman
I use the UAD platform and the difference in RTAS vs. VST of the same plug is clearer and small changes in the knob settings can be heard in RTAS less so in VST. I have file tested this and there is a difference in the files in the mid to upper frequency range.
From my experience it is a waste of time to compare DAW platforms without taking into consideration the primary influencer of the sound which is the plugins used to develop a mix. Another area which is never debated is how one DAW handles the audio driver versus another. This alone can skew your listening results even though the files of two systems can match.
Bowing out now because I have a feeling this old and worn out debate is about to tumble into the realm of my DAW is better than your DAW.
I have heard a lot of odd things over the years but this is the most off the wall thinking I have seen in a long time.
VST and RTAS are protocols only. Neither one has anything to do with the sound what so ever. The same goes for DX. If you perceive a difference it has nothing to do with the protocol used. As long as the internal processing is run using the same math and the bit depth and sample rate are the same there should be no difference. Think of the protocol as nothing more then a container holding the processing algorithms. What is important to us end users is will it work with our host?
I am not a fan of any protocol. It makes no difference to me whether its VST or DX as long as my host can load it. You should look at it that same way. Though, my first guess would be that an RTAS plugin would be more limited in how it can process due to the limitation of PTs audio engine for so many years. It has used a 48 bit integer audio engine for a very long time. I'm not sure that an RTAS plugin is designed to do floating point math.
If it does than it should sound the same as a VST version or DX. If not it is due to the RTAS protocol that is use only by PT. Why do you think PT has move away from it and now is using a brand new protocol? Could it be because RTAS can not deal well with floating point audio?