I have owned the 3.5 ACOG (TA11) and the ELCAN OS4X and they are both outstanding optics....As far as clarity, it was a toss up for me. I had to get rid of them, as I need an optic that has a diopter adjustment for my eyes....
Based on optical quality, you cant go wrong with either....BUT, the only issue I had was the ARMS mounting system that the ELCAN uses for the mount. I do not like the AMRS system at all
I could never get the scope tight on the rail, tried all different rifles in my collection, KAC, DD, LMT, Larue and even purchased the ARMS upgraded levers....save your money. The upgraded levers are very flimsy.
The ELCAN adjustmemt system is very unique, as you mechanically move the optic in the mount and not the internal reticle....I really like the scope, sans the mount but my eyes did not.
If I had to buy one again, I would go with the ACOG based on the mounting system alone
Trijicon makes a 6X ACOG but it is very big, I held one before and it is massive