I've just got a rMBP but now I'm slightly addicted and want to try an 11inch Air as well as a casual use/family on-hand machine. Now that the 2014 Airs have hit the refurb store, is it worth buying one of them over the equivalent refurb 2013 model? For instance, in the UK refurb store the 2013 11 inch 4/128 is £599 while the 2014 11 inch 4/128 is just £40 more at £639. Is it worth the extra £40 for the newer machine or should I get the 2013 and put the £40 to an external drive? Thanks!