Silicone and Teflon jackets seem to have comparable temperature resistance when it comes to dealing with a hot soldering iron. The difference that I've noticed is in jacket toughness. Silicone is softer, more pliable, but more easily cut. Teflon is stiffer but more cut- and abrasion-resistant. If you need something like 12 ga noodle wire, no doubt it'll come with silicone insulation, not Teflon.