all good options but i'd pick the dell
i own an asus pb278q - PLS - asus pb238q - IPS - and dell U2212HM - IPS
colour wise the dell has the best factory calibration. needed to spend a lot of time on the two asus ones to get the colour right. once you do they're great though
They're all very very very similar. I guess a lot of it is going to be down to which one you like the look of most. Also make sure you have all the necessary ports. Display port, HDMI etc. All use the newer IPS tech and are LG panels i believe. I mean the asus ones have a slightly lower response time which is arguably better for gaming but there's not much in it at all.
This is only the response time the manufacturer gives you, in reality they tend to be higher anyway. Maybe Dell is just being more truthful, but as others have said, you won't notice it.