Much of The Secret World is the same no matter which faction you chose to go with. The open world where nearly all of the game takes place is identical no matter which group you pick. If you’re a Dragon you can even team up with an Illuminati and a Templar at the same time. So the question becomes, if most of the game is the same no matter which side you join, does it really matter? I would say that yes, it very much matters and not for the reason you might be thinking.