Watch the GoingGear review linked earlier! Yup, they have different chain attachment, the Ti doesn't have a tail button that's the attachment point (I think).
Ti tail design allows tail-standing, something I use a lot. Copper and brass designs might be better for hanging in your pocket from a clip , or chain around your neck(speculation as I have not used either of those methods, but am considering trying them for some of my lights).
I just received mine (Ti Blue): The tail attachment design is actually more well- centered than the non-Ti, to hang straight for a pocket clip or neck chain (but the neck chain supplied grabs hair like crazy) - besides allowing tail-standing. It is very small and weightless for all practical purposes - I'm carrying mine in an extra/empty pocket for back-up - in case I don't have another flashlight handy when I need one - don't even know it's there. Good beam - no hotspot - low just a little bright for my taste - no biggy. The threads seem to be cut with the tolerances a little too loose - my light flickers on low, and it is pretty clear that the fit of the threads is causing that (but I also added lube to the threads - they had some but pretty thin). If it is tightened almost to the high beam the flickering stops. One more thing: One member (Toxic - see post/pic below) has had problems with a plastic disc installed between the lens cap and the body. I think this could be caused by tightening the head down all the way on high (not saying that was Toxic's cause). I recommend not doing that.