Well the MBA is definitely faster than rMBP 13" since they share almost the same CPU/GPU yet the retina has much more pixels to process.
As for the Airs in 2012 to 2015 production... In 2013 there was quite significant boost in battery life, then nothing at all worth mentioning till now, 2015, and we have broadwell-u chips. In comparison to 2013, broadwell i5-5250U is ~12% faster than i5-4250, however the new HD6000 GPU seems to be quite significant boost to the older 5000 series. Increased SSD bandwidth? Nothing you are gonna notice outside of the benchmarks. All in all, if graphics isn't THAT important, I would say go for the 2013 model, otherwise - 2015.
But doesn't the extra GPU / CPU mean that the Retina Pro is a much faster machine in spite of the extra pixels?