I 've got a Canton 15680 and an Armando GT40 and consider them both very good pans.
http://www.cobralads.com/enginetools/MVC-739S.JPG.html
I've never had any sealing problems with the Canton. I did have the two piece gasket. I personally consider Canton racing products to be excellent. If you don't have their catalog, you might check out a copy since some of there stuff is really trick.
http://www.cantonracingproducts.com
The reason I ordered the Armando pan is because it was almost 2" shorter than the Canton. I think I only had 4" ground clearance before and this was scaring me. The new pan should be almost even with the frame rails.
http://www.cobralads.com/enginetools/MVC-741S.JPG.html
I've heard that Ford has selected Canton as the supplier of
oil pans for their modular 4.6L engine.
Andy