First, don't forget that you can read about the 1908 No Motto Hoard story over in the RWB Saints Thread, JP.
Second, although I don't like this particular NGC holder (solid white interior), and even though I am more partial to Saints, I would probably go with the 1904 Liberty DE and wait on a No Motto.....and then, when you do want to add a 1908 NM... spend a few more $$$ and get an MS-65 CAC or even an MS-66 (or higher) No Motto.
The surplus of 1908 NM's means that you get a lot more "bang for your buck" -- premium wise, that is -- whatever dollar amount you are willing to spend. Just as both coins above are $2,300 but you can get an MS-64 for the No Motto vs. MS-63 for the Liberty.