Callahan, hands down. And not just because it made 2004-2007 blow chunks, but also because it made half our fan base so insecure and lowered standards so much that we're content with 6 wins over terrible teams, 3 lucky wins over decent teams, 2 blow out losses, and a couple more close loses to teams we should have beat. Ad infinitum.
I think you are still blaming Bill for Frank's shortcomings. The majority of those players were recruited by Frank that Bill had to work with.
That's not even the half of it.
Callahan was trying to use french to teach portuguese to a bunch of spanish kids. They may have been Frank's guys, but they were not totally incompetent. Had Callahan has the brains to pare down, or tailor, his system to the skillset his guys had and gradually instituted the transition, instead of coming in shock and awe and blowing the house up, he woulda had lots more success them first couple years, and probably wouldnt have lost the team by the end of 2004. Frank left Callahan no talent. Funny, they won 10 frickin games the year earlier.