1)Combustion: The main difference is where the combustion takes places. In IC engines fuel combustion takes place inside the cylinder, whereas in EC engines it takes place outside the engine cylinder.
2) The temperature and pressure in an IC engines is much higher than those of EC engines.
3) IC engines are made of materials that are better resistant to heat and pressure than in EC engines
4) In IC engines the piston is directly connected to connecting rod, whereas in an EC engine there is a stuffing box.
5) Efficiency is higher for IC engines.
6) Boilers are required for EC engines to store water, which is to be converted to steam. But IC engines require only a much smaller tank to store fuel.
7) EC engines, unlike IC engines cannot be started or stopped quickly, because it takes time to initiate boiling of water and generate steam.
8) IC engines are lighter than EC engines.
9) IC engines are cheaper compared to EC engines.