Hardness deals with scratch resistance, tensile strength deals with crush resistance. How hard the coating/anodizing is determines hardness, and what material the body is made of determines tensile strength.
Anodizing aluminum improves scratch resistance because the process dramatically increases the hardness on the very surface of the flashlight. But this doesn't affect tensile strength at all, the same amount of weight vs un-anodized will still deform the body.
Surefire uses a quality alloy of aluminum machined to a thick/heavy gauge, with Mil-Spec hard anodizing; this is a bang-for-the-buck combo - excellent crush and scratch resistance at a very modest price point. There are body materials that are more crush resistant, but they're notably more expensive, just as there are anodizing coatings that are harder and also much more pricey.
Most cheaper lights use a lesser aluminum alloy cut to a thinner gauge, and softer types of anodizing. These lights will scratch much more easily, and will deform under much less weight compared to a quality light.
For our flashlight purposes, titanium and stainless steel are at the high-end of crush resistance, while AlTiN and TiCN coatings are as hard-coated as metal can be made. Note that many titanium light users prefer no coating at all - while these lights scratch more easily, any nick can simply be buffed out, as opposed to a scratch in anodizing which sticks out like a sore thumb and is there forever.
