Old was analogue, would just give radar frequency and direction.
Old RWR
Sky Guardian is the same RWR from the Buc S2B and FA2 and largely the same as the Hawks. So a digital RWR that will tell you what is targeting you
New RWR
I just noticed something interesting though. Both the FRS1e and FRS1 (SQV) got the new RWR, even though technically it should just be the FRS1 (SQV)