I live in far west Texas and backpack in NM but mostly in the Southern NM mountains which vary from about 7,000 to 11,000ft. Lincoln NF & Gila NF. I have been using a synthetic 5+lb sleeping bag that has kept me warm to the high teens and lower if I slept in my jacket in the Guadalupe mtns but never trusted it go any where else since Im unsure how much colder it gets compared to the nearest local town. Anyhow I have been looking for good quality sleeping bag to use in winter but not sure If a 0* bag would be over kill or if I should just get a 15* bag.

I've been checking the weather history for a local town in the Lincoln NF and it averages about lower 30* to upper twenties for night time temp in the winter with random monthly lows in the the single digits. Town is at about 7000ft. Since my current bag keeps me warm to about the high twenties(with just base layers) not sure if I should just take the plunge and get the 0* to get a good degree difference between bags or just get the 15* which is only about a bit more then 15 degrees warmer then my current setup.

The two bags Im looking at are the Marmot Pinnacle and the Couloir

Thanks for you help.