To be honest Superman has done far more impressive things than destroying planets (which takes far less force than moving it). He has moved one (solo), has turned the wheels of Mageddon which dwarfs the Earth moon system, and has proven to exert a force of more than 54 Earths combined, etc.
As far as speed Supes has traveled many lightyears away in mere moments (far more than 100times the speed of light) and has better instant speed (speed from rest) than Glads. As far as I know Glads in not that fast from rest. He needs time to accelerate to speeds faster than light whereas Superman can do so almost instantly. This is shown when he tries to bfr Hulk by carrying him. I don't think Glads can even vibrate, which one must achieve by instantly moving at light speed (or near it).
Lastly Glads is not subject to relativity in the Marvel universe as Superman is in the D.C. universe. As one nears the speed of light their mass increases and thus it would take near more force just to accelerate faster. In other words Supes has to exert more force to accelerate than Glads.