Outerwear - how to properly choose your snowboard pants and jackets
First thing to say here is that you should buy snowboard specific gear because the cheaper jacket from the supermarket that looks warm probabaly won't be as warm as it looks. Snowboard specific outerwear is waterproof and breathable (more or less but it is) and that jacket from the supermarket is not, that means that your sweat won't evaporate out through the jacket, making you wet and cold, it also means that the wind and humidity will come in through the jacket, thus making you even colder. On top of that, it will get soaked if you are in wet conditions and probably fall apart in 2 weeks or so. But hey, anything that works for you!
Snowboard pants and jackets need to be comfortable and above all, to allow flexibility without restraining your movements while riding. Because we flex a lot, they tend to be longer in the arms and legs than ski pants and jackets, so that they don't end up in our knees and elbows on each grab we do. Large or tight? Large snowboard pants tend to allow more flexibility, but if you find tighter pants that do the same it becomes pretty much a style choice.
Impermeability / Waterproof
Is usually measured by how much water can one square meter of the garment's fabric withstand during 24 hours, usually in millimeters (mm). So the greater the number, the greater the impermeability, 20,000mm will be better than 10,000mm and 10,000mm better than 5,000mm. Some companies like GORE-TEX don't use this measurement sistem under the permise that their fabric is so waterproof and so breathabe that can not be measured by the standart sistem.
Is measured by how much water vapor can pass trough one square meter of the garment's fabric during 24 hours, usually in grams (g). So, just like the waterproof ratings, the greater the number, the greater the breathability, 20,000g will be better than 10,000g and 10,000g better than 5,000g.
Insulated or Shell?
Insulated jackets / pants are warmer, great for the cold days, while Shell jackets / pants are better for the warmer spring days.