It is easy for the comparison to come out either way depending on personal preferences because the specs are pretty close.
I did the exact same assessment as you 4 months ago and bought the MBA 13" because a) I cared about the high-res screen more than the processor speed, and b) I only expect it to last 2 years so 4GB RAM is enough (insofar as you can ever have enough RAM.)
I did the exact same assessment as you 4 months ago and bought the MBA 13" because a) I cared about the high-res screen more than the processor speed, and b) I only expect it to last 2 years so 4GB RAM is enough (insofar as you can ever have enough RAM.)