Hi Miami Mo
To my ears the AcustiX Boesendorfer sounds more Steinway then Boesendorfer, I prefer the Boesendorfer in the NI Akoustic Piano VST, http://www.native-instruments.com/index.php?id=akoustikpiano as to Steinway I still think the Grand 2 from Steinberg comes top. http://www.steinberg.net/151_1.html
It must be said though that the Ivory VST http://www.synthogy.com/index.html tends to be the prevalent standard in the professional world.
However as has been said before, it is purely personal opinion, so buy whichever suits you.
Enjoy whatever you play

Bill