OK, I did my little test. A bounced file from PT 9 is identical to a mixdown file from Nuendo 4. When phase reversed they not only cancel perfectly, but also cancel with the original, proving that both DAW engines are doing the job properly. I will do the same test with summing multiple files when I have time, so that I can see whether or not the summing engines are different.
Just did the summing test. All files are identical. So proof that there is no difference in the sound of a bounce from PT or a mixdown from Nuendo.
Therefore all differences is mix will be caused by either differences between RTAS/TDM and VST versions of plugs, or differences in how each DAW implements faders etc. However a competent engineer will always use his/her ears. so there is no reason that a mix done on one system couldn’t sound the same as a mix done on the other.
DG