The Pistons had a way deeper bench a few years back when they won the championship. They have some good young talent now but there still isn't enough experience there yet. Maybe in time but there are a few other teams that are deeper. Look at the Lakers. They don't have the best starting 5 by any means but their bench production this year is a huge factor in their wins. I would say the Lakers have a deeper bench with Farmar and Bynum and now they just added in Ariza. Their bench has outscored entire teams this season. Amir Johnson and Stuckey still have more to prove. If they got rid of Nazr like we keep seeing in the rumors and added Webber to the bench then I think the Pistons could be in the discussion for having the deepest roster. Right now there are a handfull of teams that are still deeper.
I wouldn't take New York for anything. That place is just a mess. When I say deep it's generally around 8. Usually in the begining of the season teams rotate about 10-12 but once it comes down to it for the second half and the playoffs that number generally goes to 7 or 8, which to me is what matters the most since that is what we look at for postseason match ups.