We built Simple Commerce to feel as native as possible to Statamic. We've adopted everything from the flat file approach to not being opinionated over what your front-end looks like.
But why flat files? Because they're awesome! Besides the fact that you can version control them, it's also a big plus for security as there's no way for hackers to use MySQL Injection to fetch important data from your system.
And by the way, you have full control over content modeling! You heard it right, basically the only requirement you need if to have a price field on your products and you're all set.
Simple Commerce also has first-party support for popular gateways... Right now, Stripe and Mollie are officially supported. If you need one that we don't support, it's easy to build your own gateway.