Are nylon or leather collars best? Leather seems to be more comfortable but stretches and the nylon seems to be sometimes irritating to the skin but holds its form. Are there other options?
I like nylon on some of my dogs because it does not brother their necks or create rashes. Some of my dog have leather collars because it holds them better and doesn't make it easy for them to chew on.
Collars may cause trachea collapse, I'd stick with nylon harnesses.
Nylon Harnesses are the way to go, collars can cause damage to their necks
I think it is a matter of personal preference and your dog. What I think is more important when choosing a collar is the closure. I prefer buckle collars (close like a belt) as they have proven to be a safer choice. The snap collars (like seat belt closures) can pop apart if a dog pulls hard against it, and their clasp can weaken over time. Especially if it is a plastic closure. I have seen dogs yank apart and out of these type collars. :)
Of those options, I prefer nylon (washable!), but both of my dogs currently have collars from Cycle Dog (http://www.cycledog.com/product-categ...). They're comfortable, no-stink and antibacterial. Bonus points for having a bottle opener, so the dogs can always open my ciders. I've also been really happy with Dublin Dog collars before.
In my opinion, nylon is better. Check out Lupine collars and leashes. They're inexpensive and have a lifetime guarantee to last even if chewed.