I recently bought the NX8 2.5-20X. Have had it out once and really like it. Not too heavy. Glass is very good and it is a rugged, well made scope. I have mine on a precision AR15. So far I have only shot it out to 100 but I have access to a 600 yard range, so I will definitely do some long range shooting. However, given the inherent limitations of a .223/5.56 bullet, I still anticipate 95% of my shooting will be between 100 and 4-500 yards. For those distances, shooting steel I think 20x is all the magnification I really need.
Just before I bought the scope I either started or was part of a thread discussing this scope on SH. There were a number of posters who criticized the scope. If I recall correctly the two main complaints were that it has a very tight eye box and the parallax adjustment. I chose to ignore these complaints because I was able to pick up the scope and a mount for a very good price and neither criticisms worried me all that much.
Now that I have the scope I can tell you that I didn't experience any problems with the eye box. However, the criticisms of the parallax are valid. With some scopes you can set the parallax at 200 and use at a wide variety of distances. With the NX8 you need to constantly readjust the parallax for different distances. I really don't plan on using the scope in a situation where I'm going to be engaging targets at multiple distances where I'm under tight time constraints. I can take an extra 10-15 seconds to adjust the parallax for different distances. But I can understand where this might be a deal breaker for other shooters.
As to the other two scopes, I'd say it really depends on your budget, the distances you plan to shoot and how much you care about the weight. The NX8 4-32 seems to be a very popular scope, and if you plan to shoot longer distances or want more magnification this would probably be a better choice. Also, you might take a look at the for sale section of this website, since I think there are several people looking to sell this scope and you can save some money if you're willing to buy used.
I have zero experience with the ATACR, but a lot of people really love them and I think the glass is considered a step up. But they are heavier and more $.