The Simpsons have a slightly larger diameter head, heavier shank, beefier threads and lower head profile, making them a better choice for roofing systems going under metal roofing through 9 inches of foam.

The larger diameter helps with avoiding 3/8 OSB pull -through, the heavier shank makes them less susceptible to wandering off vertical, the coarser/beefier threads are a better match for timber fastening beneath the roofing envelope.

They are too expensive. The competition's spider drive is better than the T30, but for light duty (through OSB/Foam to Lumber roof deck) drive integrity isn't really as important as other qualities. The competition is pretty much the same price. When you need 3000 fasteners, a dollar a screw is too much. Poor current availability and lack of 1/2 incremental longer size choices create difficulties when you are concerned about screw tips showing through cathedral structural T&G roof decking under envelope. Essentially had to use extra 1/4" OSB intermediate sheathing to get "enough bite, but not too much".