I don't think you can necessarily look at it like that. You have to look at the entire team as a unit.
As a unit, I'd say we're approximately equal defensively. My guess is that we're slightly better defensively on the perimeter and slightly worse defensively inside, but that's a guess.
I think we've downgraded significantly offensively, and our rebounding has downgraded significantly, as well.
As a whole, I think the team is quite a bit worse than the 2008 champions, although they've recently regained contender status.
(Also, as much as I like Pietrus, I'd take Posey over him every day.)