I have used both bladders and the Nalgene bottles on snow shoe and cross country ski trips. The bladders are convenient when you're on the move, as long as you can keep the tube from freezing. Typically, they are running down a couple of clips on the shoulder strap of your pack somewhat exposed, but, you can also sometimes route them out the top of the pack and under your hood. If the hood's attached with snaps there is usually a gap, and you can route the tube through it, and have it inside your parka, where it won't freeze. I once also routed the tube through the pit zip area on a softshell jacket to keep most of the tubing out of the cold.

With the Nalgene bottles, when on the move, I find that the splash guards they sell help you get more water in your mouth, and less on the ground, or your clothes. <img src="/images/graemlins/grin.gif" alt="" /> The splash guards fit tightly inside the wide mouth, and allow you to sip while walking, skiing, etc. The three different backpacks I use all have water bottle holsters on either side, which can be reached without having to take off your pack. I know my daypack is from LL Bean, and my largest pack is from Kelty. Most of the daypacks I see have some ability to hold a couple 1 Liter bottles on the outside.

With either choice, if it's really cold, you can sometimes avoid freezing situations by throwing a handwarmer pack into the sleeve that the bladder goes into, or into the pockets on the side of your pack that your Nalgene's are going into. It won't make the water warm, it'll just keep it from freezing for a few hours.

Overall, I find that I use the Nalgene bottles a lot more frequently, but, I think it's mostly because I hate cleaning out the bladder/tubing assembly after each use. The Lexan Nalgene bottles, on the other hand, just go in the dishwasher.