Include the jacket, pants, gloves (and somewhat overlaps with helmet, which is also a protective gear item).
Do I need full waterproofing or is water resistant enough?
While snow is more dry than rain, this ultimately depends on the weather (and your skill, if you fall a lot, you'll get pretty wet!). It's always safer to get something fully waterproof
How are outer layers specifically for snowsports different from other outer layers, say rain clothes?
- More durable since snowsports is pretty rough compared to walking on trail (e.g., falling on snow/ ice), outer layers generally are made with thicker fabric. Rain clothes don't need to be as thick, not to mention that would add to weight, and many backpackers want ultralight gear for long trips
- Features or styledesigned for snowsports for example helmet-compatible jacket hoods, snow skirts or gaiters to prevent snow from getting up into your clothes, RECCO reflectors for avalanche safety, or longer length jackets to provide more coverage, etc.
Given how important those 2 points are, it's generally advised to get snowsports specific outer layers, unless you're very confident in your abilities & already have higher end rain gear, which some manufacturers have designed in mind for more hybrid use (more durable fabric, with features for snowsports).
Should I get a hard or soft shell?
Depends on how you want to thermoregulate . Generally, if it won't be precipitating very much, and you will be heavily exerting yourself (e.g., cross-country skiing), a soft shell may be a good idea. Of course, for some people, this is also a fashion choice
Should I get bib pants?
Bib pants help prevent snow from getting down your clothes since they're basically overalls. But the decision to get them is often a fashion choice (same as with onesies)
Do I need gloves? What's better, gloves or mittens?
Absolutely! This is not an area to skimp (though unfortunately, quality gloves or mittens for snowsports are surprisingly expensive, starting at $50) because your hands will be constantly exposed (when skiing you have ski poles to hold onto). For the difference between gloves or mittens, check our general protip