1. Less seams, bigger leather pieces
For gloves fabricated from many small pieces, these tend to be remainders from making other products. These remainders are usually not from the best center parts of a hide. Besides, less numbers of seams obviously reduces the danger of something being ripped open. It is a big advantage for the inside of the gloves to be made from one single piece. Gloves with fewer big pieces of quality leather will usually be more expensive.
2. Enforced palms with sliding capabilities
We tend to stretch out our arms and hands to support ourselves whenever we fall. It is a natural reflex. In an accident case, what happens if we try to catch ourselves falling onto the road? The asphalt teethe with the gloves material on the palms, because that's where our weight is. As the consequence very often both hands are broken by the resulting high friction forces. We need generous double layers of best leathers there, with rivets on them which are to be heat insulated. The temperatures on the rivets can easily be as high as 250 C = 480 F. This is a temperature level which will fry that little flesh on the palms within seconds.
Some vendors use a heat resistant artificial material as second (or sometimes even third) layer. This material should be designed to provide the same sliding effect. It will grind down. Until the material is ground off, the sliding speed (hopefully) is reduced and the remaining leather layer will be able to cope with the forces.
3. Armour patches on the gauntlet
This armour shoud cover the outsides of the hands. and reach well over the little finger. Loosing the little finger or the palms sides is quite a common accident result. Ask racers. The plastic armor on the gauntlet itself is supposed to work similar to what is said in the last paragraph under 2. . It's second purpose is impact protection. This is a danger spot together with the lower ellbows. It is the spot we hit second most, with the palms being on the first rank.
4. Knuckle protectors / hard shells and finger armor/cushioning
This is important in case our hands are smashed onto something, like a road curb. All knuckles are very fragile, because they are basically joints that can have complicated breaks healing not well.
5. Long gauntlet that reaches well over the jacket sleeves
Obviously a too short gauntlet may be pulled down further and expose the arm. The gauntlet should be easily adjustable to be tight, so that it is impossible to pull the gloves off.
Here is an example of a "role model glove", the Held Akira:
