The main disadvantage of mittens is lack of dexterity. This means that when you don’t have your fingers free of the mitt, grabbing a pole or tool is not going to be the easiest. However, your hands will be much warmer than they would be in gloves. Depending on your cold tolerance, dexterity might be a compromise you are willing to make.
Keep in mind that sometimes mittens might be too warm, like on high-temp spring days or if you are really working hard on a powder day. Rather than ditching your mittens altogether, you can opt for a pair that has a removable liner or ones that have small zipper pockets on the top of the hands for quick, easy ventilation.