If you look at respective NBA accomplishments of the two cores right now you have to choose the Nets' core imo. But to do this you're basically comparing Nate and Lee to Lopez and Harris. The other guys' peaks are still pretty undetermined.
Two years from now, I'm not so sure. We have a player and a leader in Gallo, Hill is clearly a project, Douglas hasn't played an NBA game yet, and Chandler is only 21. I honestly think Gallo will be the best player in terms of contribution to a winning club of the bunch. Plus, I think Stutter is right. Our guys play better together and are better complimentary players (to LeBron). We've seen it several times this preseason already

The Nets are a bit further down the road in their rebuilding process (and had better assets to start with) but I'm not convinced that they even have the better core long term.
As far as free agency goes... I mean, for real... they started their rebuilding process with Jason Kidd, Vince Carter, and Richard Jefferson... 3 aging stars with value to good teams. Guys you can actually get young prospects in return for. We started ours with Zach, Curry, Marbury, Jeffries, Crawford, Q, Jerome... all these nutjobs with horrible contracts to deals with. So yeah, we're going to take a little longer and free agents are going to understand where we started from and what we're building here.