Better.
More so.
I don't know what plasma you have, but LG OLED's input lag is better than most plasmas excepting some of the Panasonic ones in game mode.
I mean, if you buy an OLED today, there will never be a display that offers a lower black level than what you will get. I'm a plasma fan and that was the line for me, each year's plasmas would have superior black level.
Caveats about OLED coming from plasma:
-motion resolution is inferior.
-near-black uniformity is inferior.
Again, I don't know what plasma you have, but I have a later Panasonic and a voltage-tweaked Pioneer Kuro 9G. My Pioneer has better black levels than any LCD ever made, and my Panasonic has black levels equivalent to the best LCDs. Where these displays look outdated is when you have an HDR version available. My OLED with HDR content looks marvelous and the upgrade seems worthwhile. If you are still consuming mainly SDR content, no LCD on the market will be an upgrade for you, and OLEDs are something akin to a sidegrade.