After spending hours manually removing duplicate images, I thought there had to be a better way. And I found it in the form of File Buddy's duplicate files checker; comparing the data fork size and contents of 20,000 images in the one folder took a matter of minutes. The next challenge was to find a way to, in each group of duplicates (of which there were routinely about 4,000), select all but one file and trash the actual duplicates.
I didn't actually find a way of doing this until I'd manually selected and trashed over 22,000 files in "page view" groups of 25-30 (5 hours' work), when in sheer desperation I went to Google and found a solution in - duhh - File Buddy's FAQ. I needed to customise the list window toolbar to add the Duplicates button menu, from which I could have File Buddy do exactly what I'd been doing manually, in about three minutes compared to my five hours. Curses. It took about ten minutes, in total, to find and trash 15,000 duplicates.
I still have to manually go through the remaining unique files from each cam and sort them into individual folders, one for each camera angle, but it's much more fun without having to worry about checking for duplicates at the same time.