Xanax bars are 2mg. Xanax 1mg XR is extended release xanax. It's probably better for anti anxiety since the half life is probably longer. Regular xanax has such a short half life.. it's great for panic attacks but not so great for long term anxiety.
Xanax 1mg XR is just extended release. I was prescribed them a while back and if I chewed them or snorted them I couldn't tell a difference between them and 1mg of regular xanax