Guy says to use the Pulse Rifle in corridors and save the shotgun for wide open rooms? Isn't that the opposite of what you should do?
Well his logic seems sound looking at how they function in the game.
The shotgun isn't using slugs so it has a large spread with each shot, so in a corridor with an alien jumping everywhere you'll hit it more. The Pulse Rifle is a rifle really, it shoots out in one direction and you can spray it but it's not that effective if an alien is constantly moving out of a line of fire, so in wide open areas where an alien has less places to avoid fire it's better to use that.
If you could use slugs and get better at spraying yeah, you'd do the opposite.