Cucumber vs TestNG : Which is better?

I have been a long time user of TestNG.  Few months back, I started exploring about Cucumber. It was a wish from my client to create automation framework using Cucumber. I searched on web & found many blogs on Cucumber & its implementation. I started with assumption that Cucumber will replace TestNG. After working for few months, I came to following conclusion they are as follows -

Cucumber

TestNG

Cucumber is a collaboration tool, which lets non-technical people write executable specifications. Those executable specifications test your app from the outside - like a black box. Cucumber is not meant to be used as a unit testing tool.  It allows to write automated acceptance tests, functional requirements and software documentation into one format that would be understandable by non-technical people as well as testing tools You can implement your tests using the same language you use to discuss them with the business.  Cucumber adds the overhead of plain English (or other native language) to executable code conversion Good for acceptance testing

TestNG are unit testing tools. They are great for testing individual classes, but not great for executable specifications that are readable (and writeable) by non-technical people. It facilitates to test individual classes.  You can group tests using tags.  TestNG supports a lot of complicated practices like priorities, grouping, listener etc.   Useful when you have to automate large number of test case