TidBITS#732/07-Jun-04... Some people put several partitions on a hard disk. The partition map tracks the various partitions. I damaged the partition map. As with the bad sectors, I performed this test on a real hard disk, since disk images don't have partition maps. Tech Tool Pro didn't detect the problem. Of the other utilities, only Norton Disk Doctor even noticed this problem, although it couldn't fix it....
... Of the 15 damaged disk images, Tech Tool Pro repaired 9 of them perfectly or well enough, and did pretty well on the last disk. That stacks up against DiskWarrior with 12 fixes, Norton Utilities with 11, Drive 10 with 9, Disk Guardian with 5 and Disk Utility with 4...
... I stick with my earlier recommendation for dealing with damaged disks. Try Apple's Disk Utility first (since it's free and isn't likely to create any additional problems), and if Disk Utility fails, hand the damage over to DiskWarrior, which has the best chance of fixing whatever ails your hard disk. And please, keep good backups!
DiskWarrior is $80. At that price I'm tempted to rely on backups and Disk Utility first, then buy it on need.
More startling to me was that nothing can repair partition defects on an OS X disk. I'd gotten the feeling that OS X and Apple doesn't really test multi-partition configurations that heavily ... I'd avoid partitions ...