My leather stockpile got to the overflowing stage a long time ago, and is growing faster than I can tailor stuff with. So I've decided it would probably be best to bulk-sell a lot of it to a trader. I've been looking at the Wiki info on Leathers (http://rimworldwiki.com/wiki/Leather) and have created this list from the stats there. Green is good and red is bad.
Armor - Sharp Factor/Armor - Blunt Factor
Thrumbofur: 3/3.5
Rhinohide: 2.5/2
(All other leathers: 1.5/1.5)
Armor - Heat Factor
Pigskin: 3.85
Thrumbofur: 3.2
Cowskin: 2.9
(All other leathers: 1.7)
Insulation - Cold Factor & Heat Factor
Thrumbofur: 1.35
Arctic wolfskin: 1.25
Lynxskin: 1.15
Pigskin: 1.1
Alpacahide
Chinchilla fur
Snowhare leather
Warg fur
Yorkie skin
Arctic foxskin: 1
Bearskin
Carribou leather
Dromedary leather
Elkhide
Fennec foxskin
Husky fur
Megasloth leather
Muffalo leather
Polarbearskin
Red foxskin
Timber wolfskin
Hare leather: 0.95
Boomalope leather: 0.9
Catskin
Cougarskin
Deerhide
Goathide
Labrador fur
Pantherskin
Squirrelskin: 0.85
Beaverskin: 0.8
Cowskin
Capybaraskin: 0.75
Gazelle leather
Monkeyhide
Boomrat leather: 0.7
Human leather
Raccoon leather
Rat leather
Rhinohide: 0.65
Elephant skin
Cassowary leather: 0.5
Cobraskin
Emu leather
Iguana skin
Ostrich leather
Tortoise leather
Turkey leather
Market Value Factor
Pigskin: 1.45
(All other leathers: 1.3, except)
Cowskin: 1.1
So, shall I start by getting rid of everything in red on the "Insulation" list, except for Rhinohide, for its armor properties?
You also might consider how much you have of each leather. No point in hanging onto 24 units of something you got from a pod drop that won't ever appear again in your biome (e.g. lynxskin in a desert). Sure it's got great insulation, but you can't even make a hat out of what you have, and you're unlikely to see more soon.
Like khearn mentions, quantity is the primary considering factor in what I keep. If it's rare and I have less than 25, it's automatically gone. I typically only keep leathers that I have large quantities of, or that I am reasonably sure I'll get more of. Also, aside from Devilstrand, I don't usually pay much attention to what my stuff is made out of; In colder climates, where I'm actually worried about temperature, I may also make a point of using wools and warmer fabrics.
I have enough to make a hat in all the leathers I have but for one, and I don't think I'll ever run out of alphabeaverskin. So I can sell a lot of it - maybe I won't need to build that base extension to house my leather collection after all!
A great, and profitable, way to use excess fur and leather is to have you best builder make armchairs. They barely take any time to make, and, like nugget, they sell high.
Pigskin is the go-to material if you don't have much to work with. For some reason is has better insulation than most common (and even rare) leathers and average-good stats otherwise. It's a minor difference though and for really cold maps, leather won't cut it.
I made 48 custom stockpiles to each accept one unique type of leather. My goal is to "Collect them All".