I need to purchase a new MBA so my daughter can take my 2012 13" MBA to school with her. I am looking at the 11-inch model with 256 memory and 8GB RAM. I am also considering the refurb with same specs and mfg date of 3/2015. Is there a huge performance jump/battery performance difference between the i5 and i6 processors? I am not interested in the free Beats headphones. Thanks for any and all advice.