People will debate they are the same.. But depending on the source there can be a difference.. I usually prefer DTS since to me it uses the surrounds with more dynamic sound. Technically it also is sampled at a higher bit-rate...
But there is one True HD track which is really good and is the best I have heard yet.. National Treasure 2 has the best True HD track I have heard yet and has the highest bit-rate I have seen for True HD tracks..