I have a LE Colt AR-15 Tactical Carbine ( AR6721) I'm looking to put Optics on it so which should I pick, Leupold Mark 4 CQ/T 1-3x14 or EOTech 550 Military Series Rev. F or Trijicon Reflex 1x24??

I can't speak for everyone but I've used the Lupy CQT and found it too big and bulky for me.  Combine that with the price and short battery life.

I am getting a Leupold CQ/T that will be going on a new DPMS 16" carbine. I decided that I wanted a red dot sight for close quarters but would also like some higher magnification for longer ranges. The Leupold seemed best for what I wanted. Short battery life does not bother me, AA bateries are pretty cheap. It is kinda pricey but compared to the ACOG It is about the same.Soon as I get my rifle and scope I will have to give a report.

I'm starting to have some hearburn with a zoom optic for CQB work.  Think about it, if you zero it for say 100yds, when you reduce the zoom to use it for CQB where is it going to be zeroed?  Which means you need to know POI at close distances.

Quoted: I am getting a Leupold CQ/T that will be going on a new DPMS 16" carbine. I decided that I wanted a red dot sight for close quarters but would also like some higher magnification for longer ranges. The Leupold seemed best for what I wanted. Short battery life does not bother me, AA bateries are pretty cheap. It is kinda pricey but compared to the ACOG It is about the same.Soon as I get my rifle and scope I will have to give a report.

I have a CQ/T (W/ARMS mount) on my Fulton Rifle and I love it. Most of the time I don't even have the reticle on, except in lowlight, and frankly, the weight is not an issue.

CQ/T: 17.5 oz
TA31: 9.9 oz

If anything, cheekweld can be dicey and needs practice when you transition from 0-3x.

If you get a good deal on a CQ/T, like $500ish, I'd go for it.

Hep

Quoted: I'm starting to have some hearburn with a zoom optic for CQB work.  Think about it, if you zero it for say 100yds, when you reduce the zoom to use it for CQB where is it going to be zeroed?  Which means you need to know POI at close distances.

Good point.

However, it's not meant to be a long range optic. If we're talking about battle sighted, CQB and mid ranges, you'll hit a pieplate at 50-200yards without issue. That's my experience.

EOtech or Aimpoint. The Leupy is too heavy and the Reflex is prone to washout.

Leupold say 600 hrs. opperation with one aa batt. with setting at medium. This aint  bad for [any]  the casual shooter.  They also offer the VX-III 1.5 - 5 with that same lit circle dot. This is attractive 5-600.00 scope. Latter one needs different [foreward] mounting however. That might not be a bad thing once done. I am trying to get a look thru one right now. My buddy has an early cq/t and It is nice.
I gotta say that what ever, in this upper range of optics, suits you, you are a well equipped shooter. I was just looking at a car with a 3x compact Acog. Narrow fov on that rascal. But after some time, I learned a bit of how to use it. Not my first choice [I am not buying one], But with some time with it, I bet I could run pretty good with it. If you like the CQ/T, and hopefully you will be able to see it before you buy it, you will be well equipped.

If you want to have a variable scope for a CQB set up  then do it  with a CQT,its not to heavy its just  heavier than a EOtech,Aimpoint,or TA31,and its not that much heavier than a TA11 that no one ever wines about,and its much lighter than most scopes found on SPR's and they are  also  carried in the field on a heavier gun as well , but if you dont have to have variable then go EO, AIM,or TA31.Anyone know or care how heavy a EOtech 512or 552 with magnifyer will be?

i use a cq/t on a 3-gun rifle and love it.

EOTech with a MAGNIFIER?  No idea what that is but my EOTech weighs next to nothing.  I think it weighed about as much as the mount i put it on before batteries...

Probably the best sight i've owned, had a trijicon, had a Aimpoint, bought this and sold off the rest.  I mounted mine on the carry handle (A2) and it zeroes nice and i can hit a 200m target 99% of the time with an aimed shot, have hit the 400m Iron target at my range maybe 50% which is about what i do with iron sights.

I have the 511 model because i liked the compact design, though the batteries lack a little more than the AA's.

If you buy a AA model, batteries are everywhere, buy a few ;)

The military model is now identical except for its NV use.  The civvy models used to not have the protective cover (you bought it separate) but now all the models come with it.  Durable as all heck too...