I don't have a preference; I've worked in low-to-none light situations in the past quite often, and I have mountain climbing training and experience. The tunnels, however, would offer a cleaner and quicker path, which, if we have to take all the materials ourselves, would be a better option in the end, loss of abilities or not. As for getting stuck with no help; well, avalanche or cave-in, either way, it'll be hard going. I'd suggest we take a flat out medic with us regardless of route.

For the wall...if there's damage inside and out, if we have the ability, it would be best to try and salvage from the building inside for wall materials first; less to carry, and we can always rebuild and even rearrange the infrastructure to our liking and at a more casual pace if the defenses are already in line. The worst part will be rigging up strong enough cabling and the like, since we won't be able to use heavy machinery or power tools to move things around. I know some folks have abilities that can go towards this goal, but it's best to look at it from the bare minimum perspective just in case that's what we end up working with. You can always upgrade if it's available. Starting something that you might lose half the tools for? Not always a good idea, especially so far out from our sources.

I'm sure I'm missing something, but I'll say it if I think of it.