Which has better rendering performance, Stackpanel or Canvas+TranslateTransform? WPF/Silverlight-Collection of common programming errors

I always use a Canvas when I’m laying out my visuals usually because I will need adjust the RenderTransform.TranslateTransform to animate in some way. A colleague recently told me that unless I explicitly need to animate I should always use the A Stackpanel because it is faster than a RenderTransform.TranslateTransform when laying out objects to the visual.

Is this true?

Anyone have any data either way?