Gloves, Mittens, or Bare
Mittens are warmer because your fingers are together. Gloves are more convenient for handling objects. If you find nice mittens, you could test them with a pen, wallet, or phone. But maybe it doesn’t much matter.
If your head, neck, and trunk are warm and you’re eating, sleeping, and exerting yourself well, your blood and body will generally be warm. Your hands don’t have that many square inches exposed to be dumping much heat.
The solution is to have gloves handy. Even thin gloves will often be enough. Climbers who climb winter cliffs often wear gloves that don’t even have fingertips, so they can jam fingers into rock slits and pull up. They stay warm because their bodies and almost all of their hands are protected, so when blood finishes passing the little bits of exposed skin it’s still warm.
Climbers of frozen waterfalls wear gloves when jamming into ice.
Here’s a trick with gloves: fold your fingers onto your palms with your glove fingers empty.
And if you don’t need gloves, why bother?