I just read one of the post
be aware of the limit if you buy with steam
In the absolute, it's rather recommended to get the license from Scirra's website/manual installation. It allows you to keep up with the beta, execute several C2 instances at the same time (Steam version allows you for only one), it has no DRM and supports better Scirra in the end (money is sent directly to them).
Scirra's store also allows you to get license and redeem them later/gift them. I don't know how this works with Steam's licenses. (Also Steam's licenses are not linked to Scirra's website/badges)
read well, lucky I didnt buy yet :D