ConnectX-2 QDR vs ConnectX-3 QDR

I'm looking at expanding my current 15 node cluster to add another 15 nodes. It currently uses the single port ConnectX-2 MHQH19B-XTR listed as QDR 40Gb/s supporting PCIE 2.0. The more recent single port QDR IB card is the ConnectX-3 MCX353A-QCBT which is also listed as QDR 40Gb/s but using PCIE 3.0. (FYI, the new nodes will have PCIE 3.0 slots).

My question is would there be any notable performance difference using the newer model? I couldn't find any performance benchmarks comparing the two.

Thanks, Chris