The Asus VS238H-P Monitor v.s Its IPS Version

That's not really an ips version, they're simply different models. VS238H-P and VS239H-P. Ips is better color accuracy and viewing angles but slower response time. In some cases ips is less contrast but that's not the case here. 5ms is still good enough that you won't have ghosting so I'd go with the ips, vs239.

It's just a different display tech. Most lcds you'll find are tn, ips, and va. The vs238 is tn. Tn is what most monitors are, it's typically cheaper but cheaper ips versions have been made and really aren't much different in terms of quality vs similar priced tn. These lower end ips don't even compare to higher ips monitors.

IPS is not really a 'buzzword'. It is referring to the type of panel that goes into the display. Most 'gaming' monitors are TN panels. These have high contrast ratios, fast response times, but poorer color reproduction and lower viewing angles (think looking at a laptop screen from the top, how the colors and contrast go weird and colors can look like negatives. IPS screens on the other hand can have a bit lower contrast ratios, slower response times and are significantly more expensive. However, they have much better color reproduction and have viewing angles of 178 degrees (basically any sane angle you look at an IPS monitor and some less then sane angles the colors will not look shifted or inverted).

The main reason to go IPS is the color reproduction. TN panels can only display 6 bit color (262,000 different shades) while IPS can display 8 bit (16.2 million). This results in 'banding' in some images on tn panels where colors are changing subtly. Instead of getting a continuous change of shade, you get sharp changes between the more limited colors the TN can show.

Some, or many, TN monitors try to alleviate the color issue by using frame rate dithering, where pixels will be rapidly transitioned between two shades that are on either side of what it is trying to reproduce. This isnt perfect though. For top quality colors, always go IPS (or OLED if you just sold a silicon valley startup and want something else to do with your money then swim in it)

A final comment about response times and contrast ratios. The numbers quoted by the manufacturers are never right. They quote some ideal world specific processing time, not the real grey to grey pixel change time. You can expect the ips monitor to be closer to 20 or 25 ms, and the TN being 10ms or so. Look up reviews, I like tomshardware or tftcentral

Contrast ratios for both will hover a bit under 1:1000. 80million or 100million ratios are dynamic contrast ratios and basically seem to be a marketing gimmick.

In the end the final word is this: If you want to spend a little extra money and value strong color reproduction but wont mind some possible motion blur in fast paced games, go IPS. Otherwise go TN.

Personally I do not play FPS games and will always choose the IPS.