Gloves for BMX cyling should serve one primary purpose: grip on the handlebars. Whether you're racing your BMX bike or performing freestyle tricks, control of the bike is enhanced, if not determined, by your connection to you handlebars. So whatever you can do to improve the fit and grip of your gloves the better.
The secondary purpose of BMX gloves is palm protection from crashes and unpleasant callouses.
The third purpose is protection from the weather, rain or cold. Most people avoid riding in the rain and cold, but not everyone. For those tough souls braving the elements, you need a glove that provides protection without compromising too much dexterity.
The best glove to satisfy all-the-above is one that is tough, stretchy, and full-fingered with strategically placed silicone for grip and/or light padding on the palm.
Some riders like padding, some do not. What every BMX rider should agree on is best fit possible is the most important variable. That's why I recommend a glove with all stretch mesh and buy a glove that fits tight when brand new.