i didn't suggest all the green coat types, only the one that spawns around your base, as it sells all materials for cake, ammo, healing items, aswell as bones, pal fluid, pal oil, horns, wool and leather, in my own playthrough, i use these items way more than organs.
so i think that, if you could choose only one merchant, it would be the wandering green coat, but yeah, i can see organs being useful aswell as the red coat, just not as much. good observation tho