I've used both as well as muskrat. I can't tell a difference. Muskrat in my opinion sheds water a very very tiny bit better, though not enough to pay more for them.
That said, I typically hunt with catwhiskers tied at the 1/4 and 1/3 marks on both sides of my nock for hunting. Catwhiskers in this configuration offer the most sound dampening and the quickest vibration reduction after the shot, are impervious to water/elements, and are cheap.
I typically have 3 strings for my bow at any given time (2 hunting strings and one practice string). All are tuned in perfectly and ready to go. I keep a brand new string in my pack as backup for hunting, and a "used" string for hunting on the bow when in the woods to ensure perfect nock fit and fresh threads. Both hunting strings have catwhiskers and my practice string has fur making it easy to ID and I like the look of fur better.
At the end of deer season, I rotate strings. I order a fresh "backup string." This year's backup becomes next year's hunting string. This year's hunting string becomes next year's practice string which is re-rigged with fur for looks and easier ID of it being the practice one. This year's practice string becomes trash. Rotating strings this way means I am ALWAYS with a good string, always with a backup string, my hunting strings always have perfect nock fit, and even if I break a string on a hunt, I still have a third string laying around for an extra backup. I costs me 1 string a year and a little string wax to keep my longbow running in top notch condition year round.