Donut reticle
The donut is pretty much designed for speed. Dont make the mistake of thinking the donut is not accurate. It is and I have achieved sub-moa groups at 100, 200 and 300 yards with this reticle. Because of the round reticle, it takes a little more concentration and focus, but it is surely capable of excellent accuracy. The donut is my favorite of the reticles, but this is merely bewcause it suits my shooting prefferences best. Another shooter, with different prefferences, will easily take another reticle, and for their style shooting it will be better. Here are some things I like about the donut. It is very quick. The top of the donut is your 100 yard zero, the center hole is your 200 yard zero, the bottom line it your 300 yard zero and after 300 yards, you can use the stadia lines inder the donut.
Triangle reticle
The triangle is my least favorite of the reticles. Its a nice, big, solid reticle, which means it will glow the brightest of all your choices. This could possibly lead to being able to use the BAC a little faster, I'm not sure though. The triangle has a nice apex at the top. This is something the donut lacks. This tip of the triangle can be used to achieve greater potential accuracy with a little less effort than the donut. However, it is a big solid retice, and it will cover a lot of your target at longer ranges, and has no refference points for hold over from ranges betweem 100-300 yards.
Chevron reticle
This is my second favorite reticle. It wont be as fast as either of the other two, because it is the finest of all of them. Therefore it will glow less brightly, making the BAC a little slower. However, what you gain is the same apex of the triangle, making your potential accuracy a simpler task. It also will not cover up the target like the triangle. You can also use the bottom of the chevron for range estimation. The area between the two legs of the upside down V is 5.3 MOA... the same width of an average human torso at 300 meters.
A few more things. The TA31F (chevron reticle) comes standard with the TA51 flat top mount. This makes it a little more expensive. The TA31 and TA31A only come with the carry handle mount. However, you can mount ANY ACOG on any flat top or carry handle. You just have to use the correct mount.
Also, the reticle on the TA31F is callibrated to be used on a flat top upper with a 14.5" barrel. The reticle on the TA31 and TA31A are callibrated to be used on a 20" carry handle upper with a 20" barrel. Some poeple make a BIG deal about this and feel if they have a flat top 14.5" barrel, they have to get the TA31F. The fact is, it matters very little until you start getting way out there, say past 400 yards. And even if you do, who cares if your point of impact doesnt correspond with the marker on the reticle? Just shoot the gun, and make notes of where it is hitting.
Last thing. These are not pick up and master type optics. they take getting used to. You have to learn their features, what they do and how they work. You have to put some time in behind the glass before you get to really know whats going on and how it all functions. But once you do, they are pretty fantastic. You will be in love.
The member who said the Aimpoint would be better for a 200 yard gun could be correct. Aimpoint is a fantastic optic. I have one of these as well and I simply love it. There is not a faster or more simple dot sight to use. Pick it up, turn it on, and you are good to go. However, its simplicity is also a limitation. There is no magnification and it has a simple dot reticle. Great for speed and ease of use, but you cant go much beyond that. The ACOGs with BAC have all of that, and much more. Once you get used to it, know how it works, and how to work it, you have an optic atop your rifle that can really expand the usefullness and capability of the rifle.
Sorry for the long post... I do love these optics!