Hi Tom,the heavier one is obviously for knocking your brains out, ouch !
The lighter one looks like it is made from a different wood, one that takes a finer finnish.It is still very strong and if you had to you could really hurt a person with it, but I think it is rather like when gentlemen carried canes and walking sticks, the quallity reflecting your position in the community.This picture is of Shona people.The knobkerrie here is almost a staff.I will get some more pictures of different ones soon>Tim