What is the best way to locally store XML in an HTML5-based PhoneGap Android app?

which is the secure and fastest method of storing and retriving data (xml file / xml content) in phoneGap Android application?

window.localStorage.setItem('xml','datastring'); / getItem();

or

using SQL DB

or

using FileTransfer

Currently I am using FileTransfer. My database get hits - consider more then 100 times per minute. Which will be most efficient way?