It's basically the same as the 509 but without the 5-way blade. The 5-way blade makes more sense on the 509 because of the additional middle pick-up where as a dual Humbucker only needs 3 to have ALL possible combinations. You only need 1 for bridge, one for neck and one for both pick-ups. With the individual switches allowing you to switch between a full Humbucker or Split, that gives 2 options for Bridge and Neck selections (positions 1 and 3) with 4 options for the position 2 - HH, HS, SH, SS - hence 08.
With the 509, you have a 5 way because of the middle pick up, B, B&M, M, N&M, N - the 09 comes from the 4 positions of the 5 way that can make the Bridge (B) or Neck (N) either a Single or Humbucker. The 509 though can't offer the B&N combo (not without modding) which would give the 4 options that position 2 offers in a twin Humbucker guitar. Its the addition of the single Middle (M) pick up that necessitates a 5 way.
Other than different positioning of the switches and Tone pot, that's really the only major difference - the volume pot looks like its very similar in placement. The 24-08 and 408 look to have very similar placement of the controls and wouldn't be surprised if its the same. The special looks more like the 509 but again that has a 'middle' pick up so it seems that the dual humbuckers have a certain placement but the ones with a 'middle' pickup (Special and 509) have a different placement.
Maybe its because the 509/Special are more 'set and forget' with the humbuckers - use these to configure your guitar for a song (like set it as a HSS or SSS before you play) where as the 408/24-08 seem better placed to switch 'mid-song', to go from H to S to H during and the tone is more 'set and forget'. Both seem to have the Volume in the same position - which makes sense.
I guess if you intend to use the switches more than the tone, then having them closer to your hand is easier - which seems to be the case for both the 408 and 24-08.