A tear will tear alongthe natural grain lines of the skin if that makes sense and so the knitting back together is more natural and therefore quicker and stronger. Also a tear will only tear as much as is needed for bubs to get through, no more......with a cut they tend go further than is really needed so making a larger than necessary wound to heal up afterwards.....the only time a cut is prfereable over a tear is if it is threatening to tear directly towards the anus...then you should go for the cut on an angle to reduce potential damage and anal fissures etc etc.......