Choice of down or synthetic bags for long hike in cold

Got that Porcupine mountain trip coming trip coming up in a week or so and I am debating which sleeping bag to pack. I have a synthetic bag that I've been using forever and has never given me trouble in the cold and a down bag that I inherited from a family member that is much lighter. I've only used the down bag on twice in cold weather. The first time it worked great. The second time was about 35 degrees, with freezing drizzle and thick fog induced by warm drizzle and a snowy ground. On this trip, the down bag got pretty damp and was next to useless. I did keep it dry while hiking, but it got wet at night. I wasn't brushing against the side of the tent, it was just condensation from the moist air.

What do you all think?? Should I save on weight and take the down bag or should I go with the one with the proven track record. The weather will be below freezing the whole time so condensation while sleeping is the big risk. Do you all think the down bag will stay dry as long as I keep the vents open at night? The one concern is that if I get wet, I'll be about 9 miles from the car. On the other hand, I'm trying to keep my pack as light as possible this time and changing the bag cuts the weight substantially. By the way, they are both equally warm when dry. The down bag is about 30 years old (inherited from a relative) and the shell is not the slightest bit water resistant.

If the synthetic bag is only slightly heavier than your down antique, sounds like a no brainer to me.

As I see it, here's your choices:

1. take the bag that is a little heavier, is trusted and has never given you any problems.

2. take the 30 year old bag that gets you cold and place it under a leaky car.

3. buy a new lightweight, warm bag with a water resistant shell.

Campmor currently has down bags rated to 20 degrees, weighs only 2lbs, 6 oz and sells for $120.

Given what you've described I'd take the synthetic bag. Depending upon where you stay in the porkies you may find damp, humid areas. On one of my winter trips there we stayed in one of the 3 sided shelters near a river, the name escapes me at the moment. The area was always cold and damp and hard to stay warm. Not a good choice for down unless you're really good at keeping it dry. 9 miles is a good haul to snow shoe with winter gear.

All things being equal, on a winter trip of a few nights or so, novice poseur that I am, I'd definitely take a down bag, although there are sound reasons for either choice.

Despite synthetics' obvious advantages, the bulk of a winter bag is somewhat unmanagable unless perhaps you're hauling sleds. One partial solution is a compression sack. But they wreck havoc on a synthetic bag's loft after a few weeks' worth of outings.

A sleeping bag cover, or very light bivvy bag, is good addition in snow and particularly with a down bag. Vapor barriers, also, do a remarkable job at preserving down loft from dampness.

I agree with Calamity's comments regarding vapor barriers and bivy sacks in general, but adding those ditties to an antique down sleeping bag (which, if it was left stuffed between trips may not loft all that well, as down does break down) would probably bring the weight on par with a decent synthetic bag.

Looking at your past experience, and thinking back to my personal experience with a "vintage" down sleeping bag(positive while hiking, far from positive while trying to get to sleep) I'd take the synthetic - better to lug an extra pound or two and get a good nights sleep -

Of course, you could always use the failings of your old down bag as justification for picking up a nice, new one, perhaps with a breathable/waterproof outter shell .... should you have the urge and coin ...

I would choose the synthetic bag from what you have, although my winter camping bags are all down and my summer bags are as well.

I have a Valandre Shocking Blue on the way for a test and hope to obtain a Peter Hutchhinson's Designs Xero winter bag soon. With this level of quality, or, my WM, FF and ID down bags, a good eVent bivy plus a VBL will keep down bags dry. But, like Fred, I would not trust that old down bag and esepcially if it has the old cotton cambric shell.

A WM Dryloft-down bag in your size, either a Kodiak or a Lynx will do well for almost all winter camping and, with care, will last a VERY long time.

The original poster says of the two bags in question: "they are both equally warm when dry."

I frequently use an early 1970s REI bag that is no where near as warm as when new, but perfectly functional given the right conditions.