Originally Posted by MPaulHolmes
Third, the high voltage input dc-dc converter has quite a few extra external components needed to make sure it will function properly. The 12v-12v option doesn't have any, so it's much simpler.
Also very true. High voltage input DC-DC converters can be as abhorrently expensive. Especially when compared to the cost of simply adding a 12V battery (of appropriate AH rating) and simple 12V charger.