What are the reasons for these two very different post mount adapter designs? I'm looking to adapt my 160mm post mount front fork to accept a 180mm rotor.

As I'm looking between adapters, I find them falling into two very distinct categories, and I'm wondering if there are any trade offs or reasons for preferring one style over the other.

The first style bolts to the 160mm post mounts with separate standard length bolts, then juts out farther and drops down to accept the brake with standard length bolts.



The second looks smaller and lighter, and comes with longer bolts and rounded washers that go through both the brakes and the adapter and into the 160mm post mount.



Here is the difference when mounted:




Would there be any particular advantages of one way or another?
While I can't find anything from Shimano themselves, this description is used in regards to the second one on a number of websites selling them (so perhaps it is in Shimano's sales literature?):


  2nd version of adaptor, lighter and better hose routing


Since this is the best I can find, I'm posting it here as an answer, but by all means if someone else finds more details post that up.