November is the pristine part of the season. The snow is deep and largely untouched, sea ice landings are sometimes possible, and you're often the first ship into a site that year, so you're walking on fresh ground. Penguins are back at the colonies and courting. What you won't see is chicks, because they haven't hatched yet.
It's the strongest part of the season for the snow-dependent activities. Camping and snowshoeing are at their best in November because there's snow to camp on and walk over, and both get harder as the season melts out.
Late November into early December keeps those strengths and adds proper sunrises and sunsets, which you lose later when the sun barely sets. Pricing is usually a little softer than the Christmas peak too.
One quiet advantage: the expedition guides are fresh. It's the start of their season and the energy is different from month five.