I think the Lakers or Celtics take the lead if either team gets a top 3 pick in this year's draft.
For now, I would say Golden State have the lead. Two supplementary stars (Klay, Lee) and a young role player with some upside at SF.
That said, I think Boston could top that offer by including one of the far off Brooklyn Nets picks instead of the 2016 first rounder. Give Minnesota a better opportunity to bottom out and rebuild. More valuable long term assets in Sully, 2014 high lottery pick and a future first rounder which could become quite valuable. Better flexibility and long term vision for rebuilding team.
Golden State's offer is more win-now with limited room for improvement. David Lee is on a huge contract. Klay Thompson is due a major payday (probably a max contract) in 12 months time. Throw in Pekovic's contract. Then probable contract extensions for Rubio and H.Barnes. That is your cap space gone. For what? A 45 win team that finishes 9th in the West year after year. The return is decent but it doesn't set them up for sustainable growth + future title contention down the road. Boston's can beat that. Less short term gain, more long term possibilities. Sort of like Orlando picking Vucevic + Afflalo + picks for Dwight over quasi-stars (Bynum, Iggy).