It's a tradeoff - if you want a fast clear gaming monitor with pure blacks, you get an OLED. If you want the clearest text and are OK with middling response time, you get an IPS.
There is also VA which provides deep (though not pure) blacks, clear text and decent response time though you get some slight smearing on high contrast edges.
Personally i prefer VA to IPS by far because IPS looks washed out to me.
