transform:translateX vs transition on left property. Which has better performance? CSS

Question

I'm making a slide out menu with HTML and CSS3 - especially transitions.

I would like to know what is best practice / best performance to slide a relatively positioned div horizontally. When i click a button it adds a class to my div. Which class is better? (Note I can add all the browser prefixes later and this site only targets modern browsers).

//option 1
.animate{
    -webkit-transition:all ease 0.3s;
    -webkit-transform:translateZ(200px);
}

//option 2
.animate{
    -webkit-transition:all ease 0.3s;
    left:200px;
}

Thanks

Answer 1

Transitions via translate performs MUCH better on mobile devices!

Edit: Here are a live demo. Transitions with translateX and translateY are much smoother than top, bottom, left and right. jsFiddle Demo for mobile devices