So Andrew 89/98, the flange on the ceramic headers are about what mine looked like, but waaaaaaaaaaay shittier. The flange itself was about the same thickness but the actual sealing flange around the port was a mangled welded mess, leaked all the time. Those black painted ones you have there have a thicker flange by the looks and should avoid distorting when tightening.
It also looks like the ports are different shapes on both headers, depending on which one you choose and which cylinder head you have you could have problems I bet. Which is yet another reason headers can suck, not necessarily always suck but could suck
That's why it pays to spend a little time mounting headers, get a good matching flange, lock bolts, ball flanges for collectors and a flex pipe after the y-pipe
Best of luck to anyone running them
EDIT: Also, if I had pics I would have done comparison shots like what you have. Makes discussing things far simpler