20 degrees Celsius difference does sound like an exaggeration though - Tom's Hardware even included tooth paste in their thermal compound comparison line up and the difference was not that huge. As you can see, the difference in temperatures across different thermal compounds roughly 10 degrees Celsius. While a better thermal compound may not improve your comfort of use (i.e. palmrest heating up) significantly, it should improve component longevity, especially batteries which are affected greatly by high temperatures. As long as your processor isn't running really hot (i.e. above 80 degrees Celsius), performance should not be affected since the processor won't be throttled.
In my experience resolving overheating issues in laptops, the dust that builds up at the vents attached to the heatpipes and the fan contribute far more greatly to temperature than the choice of thermal compound. Furthermore, disassembling to apply new thermal paste may likely void your warranty. Hence, it may make sense to pay more attention to periodic cleaning. Depending on your frequency of use and environmental conditions, dust may only build up significantly after 1 year or 2.