I prefer Garritan. It uses Kontakt Player 2 which has just gone Universal Binary. They have great support and the new version is almost out.

http://www.garritan.com/GPO-features.html

Also, unless I missed it, Miroslav Philharmonik does not tout any awe-inspiring audio demos. How do I know that these samples don't just sound like high-end synthesizers? Garritan has tons of demos from fellow users. You can hear what you are getting.

The only advantage to Miroslav Philharmonik is the addition of choirs. However, I understand that Garritan is coming out with a choir package and some may be in their GPO package. Waiting to see.