I would go with the Dell computer based on the better panel that's used for this monitor. Dell uses an IPS panel while the Benq uses a Tn panel. The Benq monitor has great feedback on Amazon and pretty much everyone that purchased one and left feedback liked it.
But as I said the better panel would win out with me and an IPS panel is a great panel.
I can say thast unless you are super sensitive to a display then you won't notice any difference , just remember that were're talking about mili-seconds.
I had a Lg 27" monitor that had a 2 ms response time and when I decided to go for the 30" display all I could find was 7 ms and higher , so because I wanted the 2560x1600 resolution and the 30" screen I went with the monitor with the 7 ms and I have not noticed anything. The only thing I do notice is the better picture because of the 2560x1600 and I average 175 fps in Call of Duty Black Opps.