3770 will be faster in most modern games and QuickSync transcode.
3930 will be faster for video editing.
Both platforms will be obsolete next year once Haswell comes out since your only likely upgrade to LGA2011 SB-E (3930) would be the only marginally faster and currently still hypothetical future IB-E. If you were asking about "futureproof" as in future upgradability, both are approaching the ends of their respective ropes.
Performance wise, the 3930 might end up having a bigger lead in the future if more games and applications start making effective use of fine threading but I would not bet too much on that.
So, which one to pick between 3770 and 3930 depends on whether gaming or editing is what you are most concerned about.