Completely spitballing here, but the SOR arguments for the E-7 over the Bombardier would be range/endurance and interoperability, especially in the Arctic. I doubt that a business jet will have the range of a 737 airframe, and while Sweden is (now) a NATO ally, the E-7 is being used by 1 (soon to be 3) of the FVEY partners - currently Australia, but later the US and UK. There aren’t too many northern airfields in Canada or Alaska that could take a business jet, let alone a 737, so any missions will be pretty long.