Molecular weight determination from freezing point depression
Molar freezing point depression  
Benzene      5.12 °C/m  
Cyclohexane  20.0 °C/m  

Molar boiling point elevation  
Benzene      2.53 °C/m  
Cyclohexane  2.79 °C/m  


I would base my argument on the constants, instead of waving hands.