The OP is asking for a file size reduction. Its already 2014 and you are still recommending 2-pass/multi-pass encoding? the preferred way to encode now is CRF or average quality when using x264 or even x265
Make sure you have 2 encode passes and you're good to go.
Anyway, for the smallest file sizes I know of (though I don't pretend to be particularly savvy here), I would recommend the x264 codec.