I play more rapid games.
rapid vs blitz
"... Most internet players think that 30 5 is slow, but that is unlikely slow enough to play 'real' chess. You need a game slow enough so that for most of the game you have time to consider all your candidate moves as well as your opponent’s possible replies that at least include his checks, captures, and serious threats, to make sure you can meet all of them. For the average OTB player G/90 is about the fastest, which might be roughly 60 10 online, where there is some delay. But there is no absolute; some people think faster than others and others can play real chess faster because of experience. Many internet players are reluctant to play slower than 30 5 so you might have to settle for that as a 'slow' game." - NM Dan Heisman (2002)
https://web.archive.org/web/20140627010008/http://www.chesscafe.com/text/heisman12.pdf
What time control do you usually use?
Some experts said "play longer time controls to improve your chess." I want to improve too but I blundered more often in rapid chess than blitz chess. What time control should I use?