the '13 might be part of the valve spring recall, which some are starting to report is a death blow to the motor. the '15 is at the 90k service interval, unless you can verify all previous things have been done, you need to assume everything leading up to and at 90k must be done. so the '15, you're looking at more current preventative maintenance costs than the '13 currently. but of course, the '13 could have more issues from being ridden harder--but that's pure speculation.
here's the recommended maintenance intervals
http://www.cars101.com/subaru/maintenance-2015.html