Ping on Mavericks on late 2013 MacBook Pro slow and variable compared to Windows
The ping on Mavericks is badly broken. The reason for this is Mavericks puts network card into a power save mode within milliseconds when there's no traffic that it considers vital, and apparently it doesn't consider pings to be valuable traffic, therefore the network card (or, rather, wifi card) goes to "sleep" immediately, and it takes time for it to do so, therefore causing completely random ping results.

I have submitted a bug report to Apple in the early beta stages of the Mavericks, but they refused to address the issue, claiming "will not fix".

So the results you're seeing are not representative of the actual network connection.