@stephen,
Great post, despite the disagreement on WSC which is something I'll have to live with rest of my life.
As with any other greats, like Warne vs Murali, Sachin vs Lara, etc, stats offer insights into their respective careers, but what to be taken as the 'clincher' is left to each one's subjectivity.
For me, Garner makes it just because despite being in a 'tough boys club' where he had to face max competition from within the team, managed to have a good record in all places he played. He was also magnificiently consistent, but by some quirk of fate, never really 'converted' his four fors into fivefors, never had a 'spell' that the world would remember like Holding's greatest over, or the magic of Marshall. But the fact that he managed to pick about as many wickets per match as that great Mcgrath, shows he did his job.
That said, I don't want to show off my ignorance further and put the caveat that am as novice as a netophile could be in cricketing matters relating to their era, and wish if some experts here, who have had the privilege of experiencing their careers first hand could throw more light. That said. I feel Garner is the more underrated of the two.