When there is a long delay between the movement of the mouse and the movement of the character on the monitor, target accuracy suffers and so does gaming enjoyment. There are many sources of input lag on computers such as wireless mice, DSL or software, which are not relevant when considered individually, but can collectively lead to a tangible lag. On the iiyama ProLite B2409HDS, the input lag fluctuates between 0 and 20 ms and is thus at an acceptable level, although it is not at the top level.
20ms is enough for a pixel to pass, you may not feel it - but it's there and it does affect gameplay. And considering that PRAD managed to record from 0ms to 20ms, I'd stay away from it. It's not a bad monitor, but for getting the best gaming performance, you got better stuff out there.
Response time on monitors is NOT input response. Response time is how long it takes for a pixel to change color after it recieved a signal to change. You have GTG (Gray to White to Gray) and BTB (Black to White to Black). I don't know ANY manufacturer that lists their input response. Use websites likes TFT-Central, PRAD.de, DisplayLag. They test these monitors to find the input lag. PRAD uses a fucking oscilloscope to measure it - you don't need to know what it is, it's just very, very precise :)
To diminish input lag as much you can, run at the monitors maximal resolution, it prevents extra processing for upscaling a 720p to fit into 1080p as an example. Disable all preprocessing functions, pixel smoothness, color corrections etc... There's often a gaming mode in TVs and monitors, enabling that removes most of these functions, always check if all were removed.
I'd save some more money up and go for a 24 inch 144Hz which you can use for both. Consoles are HDMI and majority of all computers use DVI today, so it's just a button click away to switch.
BenQ has a big selection of XL24 monitors.
ASUS has the VG248QE. Still one the best gaming monitors on the market. http://www.prad.de/new/monitore/test/2013/test-asus-vg248qe-teil7.html#B...(German site, but if you use chrome - Right click and press translate to English or whatever language you use)