Problem is both have same resolution and I think 21.5 have more ppi.. He wants to buy the 24" one but i have heard that bigger monitor will cause to see the gap between pixels and image would be not great as a small screen.. Will 24" have this problem? He use it to gaming.. Also 23" monitors are not an option..
the view sonic is a great monitor i am using a similar on to the one you posted there great monitors. so i would go with the view sonic and plus i never even herd of Benq and are you buying from the site that you link the monitors to?