var l8 =ee.ImageCollection('LANDSAT/LC08/C01/T2_TOA')
var landsat2016 = l8.filterDate('2016-01-01', '2016-12-31');
var median = l8.filterDate('2016-01-01', '2016-12-31').median();
// Load or import the Hansen et al. forest change dataset.
var hansenImage = ee.Image('UMD/hansen/global_forest_change_2015');
// Select the land/water mask.
var datamask = hansenImage.select('datamask');
// Create a binary mask.
var mask = datamask.eq(1);
// Update the composite mask with the water mask.
var maskedComposite = median.mask(mask);
var maskedComposite2 = median.updateMask(mask);
So what the difference between maskedComposite and maskedComposite2?