For most corners the whole wide line on entry > apex > wide line on exit is the quickest route by trying to use the straightest arc possible through the corner. Occasionally there are exceptions to the rule though. Hairpins for instance i find myself running wide deiberataly then turning late towards the apex and getting back on the power early, this allows you to be in a straighter line coming out of the corner therfore adding to your speed on the following straight. Dont forget aswell that sometimes you will have to comprimise your line if you are going through a sequence of corners. Running wide on exit isnt always the way forward, keeping a tight line can pay off if it means a nicer arc for the last corner that leads onto a straight.