All forms of Rotom can learn the same moves, albeit Hydro Pump, Blizzard, etc.
It all comes down to the typing.
Rotom-M has 4 weaknesses to Fire, Ice, Poison and Bug.
Rotom-M has 3 resistances to Water, Grass and Steel, and a x4 resistance to Electric.
Rotom-F has 4 weaknesses to Fire, Fighting, Ground and Rock.
Rotom-F has 3 resistances to Electric, Ice and Flying.
Type-wise, Rotom-M is much better due to Rotom-F being weak to 3 common types (Fire, Fighting, Ground) and Rotom-M has a 4x resistance over it.