Both boot types have positives and negatives. Rubber besides being waterproof do reduce the amount of scent left on the ground and low vegetation. Leathers big advantage, unless it has a waterproof membrane, is that it is vapor permeable. Any leather boot with a waterproof membrane might as well be a rubber boot as far as allowing the feet to remain dry from perspiration. The problem that leather boots presents is as we walk, the boot acts like a pump pushing scent filled air out through the leather as we step down and sucking air back into the boot again through the leather. That action deposits our scent on the ground with every step but on the plus side it allows our feet to keep relativity dry. Dry feet are warmer, more comfortable, healthier feet.
Any type of mukluk out there is made highly vapor permeable whether they are US or Canadian Army issued, Steger or Wiggy's Mukluks even the originals that the Eskimos wore. Since they allow the feet to stay drier, they keep the wearers feet warmer.
Rubber boots don't pump air into and out of the boot through it's material which minimizes the amount of scent deposited on the ground. Feet can sweat up to a cup of moisture every day. Since the rubber boot doesn't pump air into and out of the boot, there's no where for the moisture to go, although some will get pumped out the top of the boot depending on the fit of the boot. Although rubber boots don't deposit scent from our foot onto the ground or vegetation, they leave the wearer with damp feet and damp feet get cold easily. The only way to combat cold feet if they are damp is by dressing warmly so that your core stays warm and keeps blood circulating well. There is no such thing as a perfect boot.