You can use any resin you want without paying $1500 license fee to FSL, you can resale your printer without paying a transfer free (buyer), you will have full control over the printer.

I'm using everything open source so others can contribute/fix/tweak.

You're always able to move back to the FSL system by putting that BBB into your machine.

Downsides I'm not a GUI person so it probably won't be a nice GUI to start.

And no warranty. Of course I doubt FSL would warranty anything if they software screwed up and broke your printer or wasted resin.