if an FTP mitt will be warmer than, for example a Hestra Vert Cut/BD guide glove?
I would think so. Never tried the FTP, had the Hestra till I left them on a bus skiing. I’ve never found Hestra to be terribly warm. I had the race glove and the Alpine whatever that’s the same as the Vert Cut save the cuff. I won a pair of Hestra lobster claw mitts, gave them to someone who's always cold. They’ve dissapeared and were deemed not warm enough when I asked years later.
My favorite Hestra is my spring Seth Morrison glove. Very nice.
For NZ I’d try the FlyLow Ridge glove made out of pigskin which is supposed to be tougher.
For warm mitts, their Unicorn mitt, or Super mitt. Super has more insulation. 360 gms vs 320gms.
Honestly, for warmth I’d try either of those two over any Hestra mitt, and they’re 1/2 the price. I try Hestras on in the store all the time. Never been impressed for warmth. I really want to like the Hestras too. But, others may differ.