In the 172s I fly I follow the POH approach speeds, fully retard the power as I cross the numbers and then just fly the aircraft onto the runway. I couldn't tell you exactly what speed I touch down at as I'm 'eyes out' judging the flare, but I occasionally hear the stall warner go off just before touchdown. As mentioned above ground effect delays the stall and published stall speeds are 'clean air' (i.e. out of ground effect).
During my PPL the instructors seemed to teach very high approach speeds. Fine on the 1500m runway at the field I learned at, but would be dangerous at some of the short strips I have visited as a PPL.
I'd try to do everything the way my instructor suggests. You are, after all, paying him or her large sums of money to teach you how to fly: why doubt what they are telling and showing you?
Agreed up to a point. I imagine the higher speeds taught during the PPL are to add a safety margin for students, I don't really see why its necessary to add 5-10 knots over and above the POH speeds once you're qualified and proficient at landing. Surely the most important thing is getting the aircraft down and stopped safely in the distance available. 172s balloon like nobody's business if you come in too fast which could be lethal at a 600m grass strip.