I'm sure I read somewhere CS3 runs better on a Mac than a PC. Not sure if it was a claim or an actual fact.
And who cares if it starts quicker? It's how smoothly and fast it runs. If I had an old Ford Escort that started its engine in 2 seconds, and you had a Ferrari that took 4 seconds to start its engine, doesn't make the Ford better does it?
After Effects CS3 is faster in Windows than Mac OS X.
Since After effects share the same code of others Adobe products i bet that results are the same for photoshop, encore, et al on identical chips.

http://creativemac.digitalmedianet.com/articles/viewarticle.jsp?id=167680