Well, having two packs on the supply side gives you some redundancy should a pack or connection fail.
I like to have some redundancy to my RX power as well. Should something happen to one connection (solder joint break, connector comes unplugged, etc.) you'd still have one connection supplying the RX.
rcbirk21 posted a link to the order page where you can specify what type and how many connectors you want on the output side, which to me, make the battery buffer a much better option.
I guess that's why I like my power distribution board. Two A123's provide separate supply voltage that operate independent of each other as well as being isolated from each other. The 8 power board leads that plug into the RX all supply 5.0 volts to the RX.