Breathability

Breathable gloves are far more comfortable when your hands get hot and sweaty in training. They'll smell better and also last longer since your acidic sweat dries faster instead of breaking down the padding. Breathability has to do with the materials used (outer & inner) and how the palm area is designed. Leather outer is far more breathable than synthetic leather (plastic) gloves. Having a nice hole in the palm and a few holes around the fingers will ventilate better than a completely sealed-up glove.

Don't be fooled by synthetic gloves with mesh or "mesh ventilation technology"; they're low quality and still not very breathable! Some people feel mesh is actually HOTTER; it's because manufacturers put a lining to protect the mesh which defeats the purpose of mesh breathability anyway.