Verified answer

1st of all don't look at the weight look at the volume the wood chips bag size would be larger so would cover more area but in saying that the gravel will be more compact ( less air space ) and wont breakdown. the old way was to apply 100mm thick but modern way takes into account what the purpose is e.g. topdressing may only require 30mm but weed supressing will be 50mm or more

The wood chips would cover more area. They do decompose however. The problem with gravel is that it tends to get knocked out of the area you put it in, making a hazard when you mow your lawn.

Technically, the woodchips. But those decompose much quicker than gravel, so I'd go with the gravel for staying power.

depends on the size of the wood chips

56 L chips ........... spread thinly 7 sq ft

do not think the gravel would be as much

woodchips for a quickfix but longterm use gravel