I have a TA-33, 3X.
I went that route due to reports of how awful the eye relief is on the 4X Acogs.
I really like the TA33 on my carbine switching from a 1-8X USO. It really skinnied it up.
The sucky part about the TA-33 and as
@Maxwell alludes to "vision matters"
No ocular diopter adjustment on any Acog.
I usually shoot sans perscription glasses setting up my scopes to my vision deficiencies.
No good with the Acog - I have to use my glasses to see the reticle and even than its a small reticle.
Still though I find it functional and look forward to trying that set up out on a mid range carbine class.
I have another AR with an Aimpoint Pro red dot. Close in it does everything my ACOG does and I dont need to use glasses to cover appropriate sized targets with the dot. Its really handy out to 200 yards and does well on having steel make noise out to 300 - the furthest distance I have had to play with it.
I dont not recommend an Acog but really try to fondle before handing over cash.