There is some debate as to whether heated gloves or heated mittens are more warm. The only way to truly know for sure which one is more effective is to compare the two, and decide based on the evidence presented which one is more warm.
The first thing to consider is that, even in a scenario where neither one is heated, mittens tend to be warmer than gloves due to the lack of spacing between the fingers. When the fingers are closer together, it creates more friction and causes them, and the hands by association, to become warmer themselves,
However, wearing heated gloves makes it easier to handle tasks that one may be completing in the cold weather. In terms of effectiveness, there isn’t much of a difference between the heated gloves or mitten in consideration of how the clothing is heated or how warm the heating is, so when thinking about which one is warmer it might be a good idea to check the branding of the products first, But if you were to take two of the same brand and decide which one was to be the warmer ones, it is likely that the answer is going to be the mittens, as mittens tend to be the warmer of the two.
This combined with the fact that heated clothing can have the same effectiveness in terms of how well they are heated could lead one to the conclusion that, of the two, heated mittens are the warmer option. But the real conclusion in which one would be the better purchase comes from whether the warmth of the item is more important to the consumer, or the ease of use when performing tasks. If the priority is the latter, the heated gloves might be the better option.