I haven't seen any benchmarks, but I doubt you'll get a big return going to the i7, certainly nowhere near the return on investment the dual core i3 to quad cor

I haven't seen any benchmarks, but I doubt you'll get a big return going to the i7, certainly nowhere near the return on investment the dual core i3 to quad core i5 is. Macbook air is mostly going to thermally limited under sustained load anyway, so the i7 benefits are likely pretty limited.