Pros:  Biothane is a completely weatherproof alternative to leather.  It does not stretch and is not affected by temperature, nor does it mold or mildew after getting wet.   Biothane is a great product for rugged users like police K-9, military, extreme hikers or those whose dogs are around bodies of water often.  
Cons: Biothane can become slick when wet.  ​

Each leash is recommended due to its quality craftsmanship and strength.  These leads have brass hardware, metal rivets (rather than just thread), proper braiding and quality materials.  You can find cheaper leashes but when your life or liability is at the end of that line, you want the best!

"I personally use all biothane leads for tracking applications with my police K-9.  Though they become more slick than leather or nylon when wet, they don't mildew or rot in my car after putting them away.  Also, Biothane does not burn your hand like nylon can with fast tracking dogs.  I've found tying a knot towards the end of my 30' lead solves the slippery issue when tracking in the rain or through creeks."  -Matt Cox, Impact Dogs owner