When Apple killed the MBP 17", I immediately ordered the the last best late 2011 maxed-out refurb model, which turned out to be one of my best purchases ever... it's still going strong and I happily use it daily. So when Apple just killed the MBA 11", I was feeling disenchanted by announced offerings so (inspired by my successfull MBP 17" experience), I ordered the last best 2015 maxed-out refurb model before it disappeared from the refurb store, even though its specs were only a marginal improvement over my road-warrier 2013 model. I was very surprised when I got my hands on the 2015 baby that it was noticeably SLOWER in my real-world testing using an identical Macintosh HD partition. Three data points: 1) 2013 model boot time to the login screen was noticeably faster than the 2015 model. 2) However when passwords were entered at the same time, the 2015 model logged in faster than 2013. 3) Computation-heavy compilation of a big program composed of hundreds of files in a VMware Fusion Windows session was noticeably faster using the 2013 model than the 2015 one. My read on this is that though the 2015 model has a faster 2.2 GHz CPU than the 2013 1.7 GHz CPU, the 2015 must have a much slower SSD than the 2013 model (even though both have similar APPLE SSD SM512 chipset identifiers). That would account for the slower boot time loading OS files from SSD into memory before reaching the login screen, as well as the faster login process once already in memory given the faster CPU in the 2015 model. I assume the slower SSD reading scattered source files also led to slower compilation despite the faster CPU. Since my 2013 MBA seemed the same or better than the 2015 model in my own use case tests, I returned it to Apple the next day. So that's my story to anyone else tempted to go for the last remaining MBA 11" refurbs.