The in game integration is the major selling point for me. I guess they could have just opened up an api for discord to hook into, but spectrum has a very very big level of access to the game discord dosen't.

This is a pretty big deal. Not only do you have cool things like chatting to people in game from outside the game or an ingame equivalent of pin dropping in whats-app, you've also got really cool stuff like the fact that your star citizen party IS your spectrum party. Imagine being stuck in a boring day in work while your buddies were doing an epic fight for a newly discovered Idris. Sure, if they were using discord you can connect up with that, but you'll miss out on live stats and telemetry, people without mics using in game party chat, that hilarious guy who wandered into the fight.

If what spectrum are setting out to do succeeds, it will also be the first game that ties up the problem of balancing non guild members being able to communicate effortlessly that in game gives you, but resilience against crashes that out of game gives you.

Another possibly minor selling point is it's all owned and hosted by cig. Server costs and devs need to be paid. Spectrum is a support app to a money making game. It doesn't need to justify its existence as long as SC exists. Discord is currently living off VC cash. They do have plans to monetize via selling cosmetic items. But I'm having a hard time seeing skins sell well enough to cover costs and the investors' cut. They've promised they'll stay free, but they wouldn't be the first to start sliding on promises once to reality of bills set in.