They are really beefy, heavy duty for sure. If you're cutting ALOT of heavy stuff it's probably worth the extra for the T head, but still I don't know if it's necessary. Like I said, we cut a fair amount of reflective and 20mil resist on our D with no problems, I don't know if that wuld have any long term affects on the head, but so far so good. If you're unsure and the extra $$$ won't kill you, go for the T, better to have more than you need than not enough...