If the 1.4A board is a 101-AK, the batt+ goes through a via and comes out under the MCU and follows a narrow trace to the led+ wire connection pad. (same for the 105C btw) That trace is too long and narrow for 6A.
The AK-47 3x7135 board is more suitable as base for a slave board because the batt+ takes 4 exposed vias in the center of the board, if you scrape off the solder mask on top of these vias at the component side and fill the vias with solder there's effectively no resistance in the batt+ to led path.