If you watch a line on close chart, draw a line at the most recent pivot high and low. Once in a while, price will break that line, but before the bar interval closes, price will retreat and it will appear as though price never traded beyond the pivot. This means when you back test, you will not see some losing trades if you depend only on the line on close, because the pattern that stopped you into the trade is no longer visible I hindsight.
Look at these two pics of the same price action and you will see how a line on close chart does not show that a short sale would have been entered and then exited at a loss. You can only see this on the ohlc chart.
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