dmassphoto ,
If you carefully look at the two shafts you photographed, the poplar one appears to have the annual growth rings, (incorrectly called grain by some) running down the whole length of the shaft shown in the photograph and provided the sides and length we cannot see are similar it should make a "safe" arrow. ON the other hand the oak shaft has the rings running off towards the RH end, that is the annual rings come to points, These are weak points and the shaft may break here.
Craig.