Who told you so Tejinder? I have used Dell, BenQ and Acer monitors [all TN panel based] and the Dell monitors need to be calibrated otherwise they have a slight bias to blue colours, this makes the entire picture have a bluish aura on it. Not a major issue.
Depends on what you term productivity, what will you use the monitor for -- Animation and image editing / office application / Gaming and media play-back?
Answer the above queries and we will be able to tell you better, Cheerio!!