good questions mate,
the first method looks good but could be prone to a few problems, mainly with the back fill disturbing the foundations and or pushing on the columns,could mean your ground beams are difficult to place because everything has been pushed 'off square'.
other problems with such large foundation columns could be movement after the house has been built, or even by having so much concrete means more steel which could be prone to corrosion especially underground.
the second method also has problems, as the infill soil may not be settled enough and may result in movement again.
i would consider the use of piles and or spread footings on top of the piles.
