You reversed it a bit here.as far as breathability goes.... my memory fails.... presumably if the same logic as above was applied, the preferred rating would be smaller.... you don't want to sweat 5000mm of body juice before it is allowed to escape your clothes!
The DC Shoe Co. Makes some great gear. Personally, I love 'em. Exotex 5,000 is their opening price point weather protection but at that price point they seam seal all of the critical seams - meaning those seams that are most likely to leak are sealed shut with a special tape. The 5K stands for 5,000 mm of water resistance and the 5,000 g is the breathability. For most conditions that is more than sufficient and at the price you can't beat it.
The real question is what are you going to be doing in the jacket and will the basic level of weather protection be enough. If you are hard core - stay out in the rain all day 5,000 mm probably isn't going to be enough to keep you dry. If you ride really hard, hike the pipe, do the back country etc. then 5,000 g breathability may not be enough - but then that is what you have vents for!
If you like the jacket I'd say go for it - it is a good deal and should cover you in all basic conditions. If you find it just isn't keeping up with what you need next year you can invest in something with a better rating and keep this one for back up.
Make sure to wash the jacket regularily - this will help to keep the weather protecting matterials at the surface and keep the pores of the jacket open so it can continue to breath.
Layer properly under the jacket so that you have a good 'moisture management' system going to aid in with breathability.
If you need help on either of these points or have further questions on the jacket you know where to find me!
cheap set of polyester long underwear tops and bottoms for your base layer. Polartec pants and long sleeve shirt for your insulation layer and your jacket and pants for your outer shell. Ditch the polartec if its a warm/hot day. If its not hip/cool enough then a triple long cotton t-shirt and hoodie with a beanie and just put up with being cold and wet.What do you recommend for layering under the jacket and pants (specifically in Arizona)? It's my first time snowboarding and I don't have a lot of money to spend on gear (already bought pants, jacket and boots). Can I wear an Under Armour short-sleeved, crew neck shirt with a long-sleeved, cotton crew neck shirt over it, and a fleece jacket over it, and my 10,000mm jacket over that? Is that too much? What brand would you recommend for undergarments and socks, or what characteristics should I look for in those?