One real difference, in my receiver at least, is that there is no dynamic compression offered when watching DTS movies. This usually means that I end up watching a DTS movie with the remote in my hand so that I can quickly change the volume when the sound becomes too loud or too soft. Additionally, movie events such as gun shots, car accidents, explosions, etc. become ear shattering. Because of this, I usually watch my movies in DD mode and using "standard" compression.
I couldn't tell you what the differences are, if any......all I know is that when I'm buying a DVD, two things I look for are 1) widescreen format, and 2) DTS track. Number one is a must have, of course, and even though I can do without number two, I still get excited when I can watch a flick in DTS......even if it's just some dialogue driven drama with little use of the rears. I just like it better!
There isn't a difference that I care about. I would rather have the bandwidth available for video than a DTS track. I used to have DTS capability and now I don't and I don't miss it at all.