The TA11 ACOG has more eye relief and requires less precise eye placement to obtain a sight picture compared to the TA31 ACOG in use by the US Military.
Low-power variable-magnification Type II optics improve close-range target acquisition speed at their lowest magnification setting; the closer to true 1x the better. The goal of these variable-power scopes is to provide the speed of the Type I optic, but still the target ID and distance capabilities of the Type II optics. The price for this flexibility is paid in increased purchase cost, less durability, and more weight and bulk on the carbine.
For small but practical targets, such as a ten-inch plates, the Type II optic will limit engagement distance to 350-450 yards, where the coarse BDC, thick reticle lines, and low magnification inhibit the ability to achieve the correct point of aim and a clear sight picture.
Although the 3.5x magnification of the TA11 ACOG is slower for close-range engagements, with training and practice the difference can be slight. The author hammers a target at 20 yards while on the move.
Schmidt and Bender's 1.1-4x20 mm Short Dot provides almost true unity magnification at the low end, and useful four power magnification at the top end. Its first focal-plane reticle has hash marks every one-half mil, and a center illumination dot which is quite bright at the 11 brightness setting. The Short Dot retails for about $2200, and almost perfectly bridges the gap between Type I and II applications.
The killer feature of the S&B Short Dot is that it is almost as fast and flexible as 1x red-dot optics at close range and one the move.
Leupold's Mark 4 1-3x14 mm CQ/T has close to unity magnification at the low end, but only 3x at the top, less than the Short Dot, TR21, TA31, and TA11. The reticle has no BDC features and its illumination is not bright enough to stand out in daylight. The CQ/T is criticized for bulky size and narrow field of view. Market price on the CQ/T is about $700. The Leupold Mark 4 1.5-5x20mm MR/T is similar in concept to the Trijicon TR21 and the Short Dot, though its low end magnification is higher than either. It does have a reticle-based BDC for longer shots. The 1.5-5x20mm MR/T sells for about $850.
The Leupold CQ/T has been criticized for being large and it lacks bullet-drop compensation features, however, it can still be used to make hits at 300 to 400 yards using Kentucky hold-over.
In the Type II or DMR role, the Short Dot is the most versatile but also the most expensive choice, more than twice the cost of any other. The Trijicon TA11 ACOG has bomb-proof construction, a compact package, good reliability, fast target acquisition due to its super-bright reticle, and, though fixed power (3.5x), is the second best choice for intermediate engagements. It gives up a little speed at very close-range engagements.