For most assault rifles electric is pretty much the only way to go. You can find some old and a few newer gas rifles but they are pretty rare in Canada and parts aren't easy to come by.
So pretty much for your main rifle your most likely going to be looking at an electric gun
a sidearm will most likely be gas although TM's AEP's are nice.
sniper rifles can be ether gas, electric, or spring depending on the gun and what role you want to fill with it.