Given the choice of a Daniel Defense or a La Rue Stealth 16" complete upper with rails which one wins?  Cost wise, they are nearly equal.

Kind of choosing between a light blonde or a dark blonde..Did you ever have to make up your mind?

BS Free Zone...VA-gunnut

No question about it...Larue hands down, I have a 16" Stealth and just got my DMR.
Both are drop dead accurate and exacting pieces of craftmanship....and you get schwag to! Intresting tidbit, my wife is on a sunbreak down in Phoenix visiting her son who is with Phoenix PD as a training officer. He commented on the Dillo (green one) on
her key chain....said the least thing he'd expect to see on a 61 year old woman's key
chain is a Larue dillo.
Midlength

Flip a coin.  

BS Free Zone...VA-gunnut

I have never owned a DD upper, but went with the Stealth based on known quality of LT products and their second-to-none customer service.  
BS Free Zone...VA-gunnut

LaRue

both are quality pieces i am sure, but i went with the laRue stealth

I own both and prefer the LT Stealth.

I am gonna say LaRue, if I'm allowed to.

OK, I'll repost most of my original post. The technical part.

I have had my hands on several LT Stealth uppers. No DD as of today.
Of the LT's, I have shot two (2).
They were shot utilizing a tight fitting Wilson Combat lower, a worked JARD trigger that releases with no take up or over travel at 17 ounces.
I attached my favorite test mule scope, a weaver T-36 Target Dot scope.
All groups were five (5) shot groups with no fliers called. If I shot them they counted.
The ammo was all my hand loads. Consisting of Winchester .223 brass. Every piece of brass of inspected, cut, and deburred prior to loading.
All the bullets inspected, weighed, and sorted by weight
Match primers and match bullets.
Will not give any load data for that is frowned upon.
All groups were fired by me at my house. A known 100yard range was utilized, taped and lasered.
Firing was done off a concrete "picnic table" that I have leveled and set soundly into the ground.
The rifle was bagged front and aft. Squeeze bag in the rear.
Each upper was shot using a "strong hold" and "no thumb" technique.
Wind flags and Anemometer were utilized, although there was no perceived wind. I don't remember the exact temperature and humidity as these were not my uppers so the data was not logged into my books.

Most grouped were in the high .3 CTC to low .4's.
I do not know if I could approve on that with load development for that particular upper or uppers.

Opinion time;

If your looking for a upper for great accuracy and very good reliability, I should think you are well served with a LT Stealth.
Albeit, this is not a upper with which you should do Beta mag bump firing into a ditch with.
The fine accuracy will be lost with total neglect of it's purpose and function. A SS barrel can be shot hard, but if you getting it hot enough to light cigs off the barrel you will lose  accuracy. I think it's a combat rifle with great accuracy potential.

Still opinion time;

I have planned to purchase a LT Stealth upper for it's outstanding attributes, hopefully in the near future. Just wish they had a LEO discount, wife likes expensive guns too, or a poor farmer discount to which I would apply. That rifle wearing a Eotech with LT mount with a LT mounted Nikon Tactical 2.5 x 10 illuminated mil dot nearby, would replace my patrol vehicle AR.

Facts:

I have not shot the DD upper, just the LT. I am making a consumer choice based on the several LT's I have seen and the two (2) I have shot. With similar reports of accuracy from the owners of the ones I have not shot. (Opinion; The other owners report groups in the .5's, ,6's, and .7's. I believe this is due to skill level,  ammo and equipment utilized. Neither of them utilized a 36X target scope, a very light crisp trigger, nor anally prepared hand loads. I have been a BR50 shooter for many decades which may have helped me.)

Maybe someone can give similar results of tests run with a DD upper.

curiosity.