As expected you got two totally divergent opinions on this one. Any blanket statement such as something being 'the best' is simply an unbalanced and incomplete opinion. They are two different products, clearly, and each have their merits and drawbacks.
With the Dell you get arguably superior build quality and a greater level of stand adjustability (height, tilt and swivel rather than just a somewhat stiff tilt). You also get a product supported by a larger and better known company with an extensive track record for having some of the best Display-related support in the business. The backlight also offers a broad colour gamut which for your uses means that you can greatly enhance the image vibrancy. Problem is none of these game titles actually support this natively so you may find certain colours or scenes become oversaturated and it will be a matter of taste as to whether this will be a problem for you. The Dell also has a high-haze matte anti-glare surface (~ 35% haze) which massively reduces glare and eliminates screen reflection whilst also diffusing light the monitor emits (and combining it with diffused ambient light).
Now I haven't had much experience with Hazro and I have been reluctant to advise businesses and other people to use them as a supplier because of this. I have found them to be very prompt and articulate with their responses to my questions, though, and I am thinking of buying a few HZ27WCs for some lab computers. The product itself has a nice construction and a 'look and feel' that some people find very appealing. Aside from the Hazro your only real choice for a 27" glossy display is the Apple Cinema Display which was never designed for PC use and is considerably more expensive and less responsive than the Hazro. The WLED backlight is restricted to roughly sRGB in terms of colour space (compared to the U2711's roughly Adobe rRGB colour space) but the screen surface doesn't cause the same kind of interference with light emitting from the monitor. The clarity of the image and vibrancy of the colours (compared to U2711 operating in sRGB mode) is noticeably superior at the expense of reflection on the screen of ambient light. Unlike the U2711's native colour gamut modes you don't get the same extent of oversaturation of certain colours (reds and greens in particular) but kind of get a general increase in 'image pop' (as Eric Franklin would put it). I know this may sound a little strange and like some theoretical or marketing rubbish but I have had considerable experience with different screen surfaces and can tell you that this is absolutely noticeable in practice. Input lag is of course lower on the Hazro but this may or may not be a problem on the U2711 depending on sensitivity.
Just some food for thought.
