What's the difference between underscore clone() and simple '='?

It's about best practices when you need to copy object in javascript..

For example:

I have an object { name: 'Dodo', method: function () { console.log(this.name) }};

I need to create a copy of it:

var obj = { name: 'Dodo', method: function () { console.log(this.name) } };
// what is better?
var copyUnderscore = _(obj).clone();
var copySimple = obj;

What is the better way? Thanks!