The big difference is that SC instances will be hosted by a dedicated server in a data center with performant connectivity.
ED's P2P model means you're at the mercy of whatever bean-tins-on-a-string network connection your peers are on. The experience hasn't improved since PB1, sometimes it's fine, but enough times the game becomes unplayable and you have to log out and try a new instance.
You'll be at the mercy of the FD system that matches peers which isn't live yet. Hopefully it's coming soon. Hopefully it'll make people in Utah on dial-up play with them self.
Pun intended.