Short-style ski underwear bottoms end at the upper thigh or hip, giving you minimal coverage but maximum ventilation. They're a great choice for spring skiing when temperatures are mild and you're working up a sweat, or if you're wearing a ski skirt and want less bulk underneath.
The trade-off is that you get no leg insulation—only moisture management for your upper legs and core. On cold days, your legs will feel it, so this style is really best reserved for warmer conditions or high-output touring where overheating is the bigger concern.
If you run hot, ski mostly in mild weather, or want something under a ski skirt without extra fabric, short-style bottoms can be a comfortable option. For most typical resort days in winter, though, you'll likely want the coverage of 3/4 or full-length base layers.