[Leica] Strap fastenings question

[joe-b at clara.co.uk (Joe B)]

There seems to be (at least) two different kinds of metal endings to the
Leica strap for M cameras. One is longer than the other and looks like a
mushroom in shape; the other looks more like a circle but with the ends
crossed over one another. I'm curious to know if one of these is
superior to the other. 

Some M users put the ordinary circular split rings in the strap lugs and
use a strap on those instead. How much of a good idea is this- do people
actually do this out of preference?

Many thanks, 
Joe B.