I recall when reading up on the pro 9 improvements that the audio engine had been revamped and improved. I tend to scoff at claims such as that.
Today, for grins, I exported the same project from 7.5 and from 9, and totally unexpectedly the two mixes sounded significantly different!
The difference is primarily obvious in the way the kick drum sounds - it’s louder and deeper sounding in the Pro 9 render. I am not sure what to do with this information to tell you the truth. The 7.5 mixes are potentially final mixes for some clients, and if I decided to go with the 9 sound, I’d probably have to turn the kick down a little in all 12 songs.
I’m interested to see if other people hear this, and also would love to hear from anyone in the know as to what was changed and why.