- Spree does not offer media management as a CMS function
This is true, but we do have some extensions such as spree_static_content that do provide the ability to create extra pages for your site.
- One page checkout is available on Magento, but not Spree
Assuming you mean the fields are all on one page: This is not provided by default, but it is relatively easy to customize Spree to do this. It's pretty commonly requested, and so it might be a good idea for us to provide a guide on how to do this.