Opinion:
The NWT actually loses some of its punch where it tries to be overly literal. The old KJV is matchless in the way it conveys its message concisely and poetically. Compare a couple of proverbs:
Prov.26:5
KJV - "Answer a fool according to his folly, lest he become wise in his own conceit."
NWT - "Answer someone stupid according to his foolishness, that he may not become someone wise in his own eyes."
Prov.26:16
KJV - "The sluggard is wiser in his own conceit than seven men that can render a reason."
NWT - "The lazy one is wiser in his own eyes than seven giving a sensible reply."
The NWT's dryness forfeits some of gist that comes with good rhetoric in the psalms and proverbs, to my thinking. Not that I am a great fan of the Authorized Version, I just like the old English for a few things. On the other hand, the literalness of the NWT is much better for rendering something like "hell".