I can't answer if the durability is different, I'm assuming it's not otherwise Cerakote probably wouldn't give the option. I have seen where thinner metal pieces like an EoTech hood had a slightly different color than an AR upper and lower at 300 degrees. This was Magpul FDE and the hood came out a little darker. I'm not sure if I had it too close to the heating element but I redid it at 250 degrees and it came out fine. I prefer to stick with 250 if I have the time, but I haven't had too many troubles with 300.