Competition skis or racing skis are normally offered with three different types of ski base: cold ski base for cold, hard and abrasive snow conditions, wet ski base for wet, soft snow conditions with water film in the interface and universal ski base for transmission snow conditions between cold and wet.
Ski base compositions differ in used additives to comply with different snow conditions.
Soot or carbon black in cold ski base types is used to increase hardness, wear-resistance.
Graphite in lamella form in cold ski base types is used to improve gliding features and electric / heat conductivity.
Metal oxides in cold ski base types are used to increase hardness and wear-resistance.
Molybdenum disulfide in wet ski base types is used to improve water and dirt repellency.
Wax like additives in wet ski base types are used to improve gliding features.
Are the different additives used in cold and wet skis the main difference between cold and wet ski base types?
I would say NO, they aren’t...
I would say that the main difference between cold and wet ski base types is the different ratio of crystalline and amorphous regions and the different wax intake capacity.
UHMWPE which is the main material used for production of racing ski base types is a semi-crystalline polymer which consists of crystalline - for waxes and any additives inaccessible - regions and amorphous regions where the most additives are allocated and where wax is connected with the ski base. Crystalline and amorphous regions are normally separated by transsition regions which are - compared to micron-sized crystalline and amorphous regions - in nanometer scale.
Cold ski base types have the majority of crystalline regions which are harder, compacter and more wear-resistant, but cannot absorb any additives and waxes (thus they are more or less pure UHMWPE), wet ski base types have higher fraction of amorphous regions which are softer, modified by additives, contain cavities to absorb waxes...