Glucokinase has a lower affinity to glucose than hexokinase, and also, glucokinase is present mainly in the liver. I don't know the difference in their molecular structures, though.
Hexokinase catalyze Glc and Fru. Glucokinase catalyze Glc only.
Glucokinase has high Km value for glucose than hexokinase and is mainly present in liver unlike hexokinase
Hexokinase has a higher affinity to glucose whereas glucokinase has a lower one. This means Gk has a higher value of Km than the other. This means Gk works when glucose blood concentration is high. Gk acts like a sensor. It 'sensorize' wether glucose blood concentration is high. This is the reason why this enzyme is located in liver and pancreas.