Like most people, I like DTS over DD.  Some of the newer DVDs are coming out with DD 5.1 and DTS 6.1 (either discrete or matrix).  For example, the LOTR trilogy and Gladiator.  My question is whether it makes sense to choose the 6.1 DTS track instead of the 5.1 DD even though I am only set up for 5.1. 

It probably comes down to how much the engineers are sending to the back channel (which I wouldn't know w/o a back channel) but I wanted to know if anyone else had the same dilemma.  Thanks.

DTS ES is backward compatible to a 5.1 system.  No information is lost when played on a 5.1 system.  First off, most DTS ES tracks have a matrixed back channel.  This means that what is played on the rear speaker is derived from what is sent to the surrounds anyway, so in essence it really is a 5.1 track. 

There are a few discrete DTS ES tracks with a real distinct rear channel.  However, even on those, your receive should simply send the information from the rear channel to the side surrounds. 

So, if you like DTS better feel free to go with DTS ES on a 5.1 system.  Myself, I do think DTS usually sounds better but I wouldn't say that it isn't the power of suggestion.  The biggest difference is just how the two tracks are mixed (they usually are seperate mixes) and there isn't any reason to think that DTS will be mixed better than DD every time.

actually, I have found DD to have better sound than DTS. But I wonder if this is because of the receiver. Is it possible that some receivers are better for one than they are for the other??

Nick, that is an interesting question, I have wondered that as well, mostly about THX certified receivers (and speakers for that matter as well).  THX certified gear doesn't mean it's neccessarily better than non-THX certified, but I wonder while working towards those specs, both the end listener and sound mixer/prodcuer are hearing closer to the same thing?  I think it's a long shot to say that, but...

I normally prefer DTS over DD, but I wouldn't say it is ALWAYS better.  As the the 6.1 DTS discrete, I had a 7.1 system before, and the biggest 'discrete' benefit I heard was on the Gladiator disc mentioned above.  When they walk Maximus out to execute him in the morning, when he throws his sword at the last main gaurd, it comes in right over your head!  Very impressive!  Having watched this same section in a 5 channel system, I can't honestly say that, while impressive, not much is lost without the 6th channel.