As RL mentioned, one of the biggest reasons to use welding cable for automotive applications is the jacket. It is usually made of rubber, almost always a double jacket, and resistant to heat and chemicals. It's also usually flexible in all temperatures. It has larger strands of wire than audio grade power cable. Some people will quote the skin effect on power transmission as a reason to use finer stranded cables, but they usually don't realize that effect happens around 15kHz and power transmission from a battery far lower in frequency than 15kHz.
Use quality welding cable of at least #2 and you should never have a problem, especially for that 10" stretch between batteries.