Cost isn't but flexibility and ease of use are. At this short distance, as was mentioned, voltage drops would be minimal. Mind you, much smaller cable is rated for amps needed to turn over the engine. My 4 cylinder yanmar needs only about 40 amps to start, but even assuming 100 amps and only 1% (!!!) voltage drop, a 2 feet roundtrip interconnect between batteries could be made with AWG 6 (I am using my own calculator from here: AWG by wire length/amps calculator
but don't trust my data, find your own). So, any larger size and voltage drop becomes virtually nil.
In my case, I used size 2 battery interconnects because they were handy and I had to do a few longer runs that required this size.
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