Block 2 SH is pretty different from Block 1, with very, very much improved avionics. That said, a lot of that is not obvious to the pilot and non-avionics aspects are pretty much identical.
The Kopp/Goon gang have done a good job of laying a smokescreen by talking about upgraded F-111s (a potentially wonderful aircraft but a potentially horrible program to execute) and F-22s (not versatile enough, not long range enough, too expensive and unreleasable).
The real problem is the termination of the competition. Hell, at this point Australia could realize some serious gains by pretending there was a competition, just in order to get better terms. At the moment they are committed to buying something with a very uncertain price tag and no firm offset commitments.