In my post below I noted that The Box has both DTS-HD MA and Dolby TrueHD encodes. I added The Broken as well. In both cases, the TrueHD encode seemed more efficient space wise: significantly in the case of a 24 bit encode, and very slightly in the case of a 16 bit one.
In comments Craig pointed out that Close Encounters of the Third Kind also has both forms. In fact, it has three of them since there are three different versions of the movie (via seamless branching). All are 5.1 channels and 24 bits, but the Dolby TrueHD’s core of standard Dolby Digital is only 448kbps rather than 640kbps.
For the Original Cut, the TrueHD comes in at 3667kbps (=3219+448) while the DTS-HD is 3768kbps. For the Special Edition it’s 3652kbps vs 3760kbps. For the Director’s Cut (Spielberg’s final word on the subject), it’s 3639kbps vs 3743kbps. So, once again, TrueHD is slightly more efficient, although not by very much. Had a 640kbps core been used in the TrueHD, it would have gone the other way.
Finally, also from Icon Film Distribution is a New Zealand/French co-production called The Vintner’s Luck. This has both lossless forms, 16 bits only, and 448kbps only for the TrueHD core. Total for Dolby TrueHD is 1646kbps, while the DTS-HD MA audio is rather more at 1780kbps.