bitcoincharts - probably most accurate data, they ask old mtgox's api (polling)
sierrachart - uses bitcoincharts data, but bitcoinchart is serving delayed data (20 min?). So using websocket (if it works) is definitely better solution.
mtgoxlive - because websocket is broken?
sierra charts 0.3 -w websocket is delayed vs mtgoxlive next best vs bitcoincharts direct the best.