The TA01 has red illumination, where the NSN has amber.  I much prefer the red, as it doesn't wash out against most backgrounds, where in my part of the country, the amber reticle isn't great against all of the grass-covered hills.

The only other significant difference is that the NSN comes with the backup sights, which ARE pretty worthless.  It also comes with the flattop mount by default, but of course the same mount can be bought for the TA01.

-Troy

I know that this isn't quite the reply you're looking for, but, I'd seriously consider this:

Don't buy either.  Use the money from the postban BM and the ACOG to buy a preban.

Preban BMs or Colt (and most others) are only going up in demand and price.  They are also much more prone to being involved in future legislation to ban getting them.  Buy one now.  
I'd guess that in a few years, either because of legislation or because of increased demand driving up prices, getting a preban will be pretty tough.  The scopes will still be available, and you can save up money for one of them later.

But, if you have to have the postban and an ACOG, don't waste your money on a NSN.

Quoted: Troy, How big is the red reticle?  Is it as small as the amber NSN reticle?

They are the same, except for the color:



-Troy