Including titanium? Because I can say this for sure: At the same temperatures (glowing orange), titanium wire forms a heck of a lot of oxide, some of which comes off the wire spontaneously, while Kanthal forms almost none, and what Kanthal does form seems almost impossible to remove from the wire.
Of course both oxides are more-or-less irrelevant if we take your advice and don't torch or dry-burn our wires because the wires will never get hot enough to forum them. The thing is, I would like to get more than one use out of a coil, which means I want to dry-burn it to clean it, and my initial experiments indicate dry burning titanium produces totally unacceptable amounts of titanium dioxide. I would also prefer to use a "micro coil" (really a contact coil), a geometry that unoxidized wire seems unsuitable for.
As for bio-compatibility of Kanthal: We're not making implants out of it, we're using it as a heating element.
FWIW, I didn't start experimenting with titanium wire because I was worried about safety with Kanthal; I wasn't and I'm still not. I started experimenting with it because I was interested in making less massive coils that would heat up faster. So far, I've not succeeded in making anything that works as well as a micro-coil made out of Kanthal. But I'm not done trying yet.
