Here's the penetration results of a heavy dart vs a light dart.  The light dart is 5 feet 11 inches, (1.8m) and 3/8 inch across, (1cm).  The heavy dart is 7 feet 5 inches, (2.3m) and 3/4 of an inch thick (2cm).  Both have two primary wing feathers from a Canada goose about 6 inches long (15cm).  I wasn't able to weigh them but the heavy dart is a LOT heavier.  Neither had a point, I just cut the end at a roughly 60 degree angle.  I threw with the same atlatl, which is made from the base end of the larger piece, it is 26 inches (66cm) long.  I threw at 10 meters, measured.  I threw each dart 20 times, I actually threw more but I didn't add in the results of the poor throws.  I threw at the end of a large, round hay bale.  

The light dart, on average, penetrated 6 to 8 inches (20cm).  The heavy dart penetrated 13 to 15 inches (38cm).  I didn't throw for distance, I suspect that the lighter dart will go a lot further.  At the end of the test, it was a lot easier to throw the lighter dart, I had to work to throw the heavier.  

If the penetration in hay were exactly equal to penetration in flesh, the lighter dart would work, barely, for hunting large game.  It would penetrate deep enough to pucture a lung of a white tail deer, which would eventually kill it.  But that deer would run a long way and that increases the chances of not finding it before it spoils or something like a bear or wolves ate it.  I really wouldn't want to try anything larger like an elk or moose and bear, black or brown, are out, unless they were trying to eat me.  The lighter dart would work fine for small game up to turkeys and geese.  

Mythbusters did pretty much the same thing, the penetration in geletain was pretty much the same.  Tissue is very elastic, the point with the cutting edge tends to cut veins, arteries, and organs, the round sharp point tends to shove them aside unless the very tip of the point hits them.  And what kills is blood loss, so the point with sharp edges usually kills quicker.  That is balanced by the ease of manufacture of the fire hardened round point.  


In my opinion, when the first people discovered rivercane, they must have thought they were in heaven, without having to die to get there.  Easy to straighten, the edges of the point are sharp so you don't have to add a stone point, and it is really tough and plentiful.