In the top image current has to travel through 1 cable between the "bank" pos and neg. In the bottom image it travels through 3. If all you are doing is running led lights at night and charging off a 100 watt panel, who cares. Put in a 60 or 80 amp (or larger) charger, or an inverter large enough to run the microwave, and the batteries with the shorter runs will take more of the load then the batteries with the longer runs. You can overcome this with very large wires, but usually banks are wires with #4 or smaller..
I have 3 12 volts, with 4/0 interconnects and leads to my inverter/charger.
