Well, to be honest, on the new mac's I don't know this for sure.
Although some producers told me that they prefer to work with sx inplace of logic because of the sound.
But on the pc, logic is a joke in comparing sound with cubase or nuendo.
However, since we have a lot of songs made with logic (emagic user for 15 years) we will invest in a mac G5.
Also because we like finalcutpro and dvdpro.
But our main system in the studio will be nuendo.
I did a few omf exchanges from logic mac to nuendo pc and that works pretty good.
And again if I listen to the same song running on logic/digi or nuendo it's such a huge difference in quality.
I'm aware that digi is responsible for a big part of this.
I have heard also the HD system and ofcourse I have to admit that it sounds better then my mix++++.... but as a digi user for 10 years I'm used to hear always from digi that the next hardware exchange will give you more power and better sound quality. yeah right.
But HD sounds still not better then nuendo.
I even begin to believe I can mix in the box................