You can't compare these two machines because they are totally different Tech, One is a Hi Speed machine and the other has a very high discrimination level that is fine tuneable,
Neither one is better than the other and you just because one costs more does not mean it's better or because one is cheaper does not mean it is not as good, They both have their areas where one excels over the other,
You can't buy either machine by asking which one is better, First off you need to be exact about you intended needs/usage of the machine and only then can you say which one is better, But that only applies if you have been honest with your self about your intended use for said machine,
If you wanted to look for Gold or high value targets like coin etc in hi trash areas then you would need the NOX, but is you wanted to look for coins and jewellery and beach detect for those Items then the CTX would be the better Choice, Then just to bugger the thought patterns up you then have to factor in Ones state of health and Age, then add to that do you like playing with computers and programs or do you want a machine that you can switch on tweak a few setting and get in to it etc,
Get one thing straight Neither machine is better than the other and neither machine is doing anything we couldn't do 10 years ago, The question you should be asking "Your Self" is which one will suit me Best, There's No bad machine, There's Just the wrong machine or Bad Operators,
Buy with your Head not your Heart and Match the Machine To your intended Task,
That's how you buy a Detector, Anything else is just BS or one upmanship trying to up stage the next Guy and doing that will result in your Tears and no one elses.
Hope that helps.