That's exactly what I did (I was aware enough of IRC ettiquite that people idle in the rooms but may come back sometime later & answer): ask a question and usually answer my own question and quit without a response some 4 hours later.
Which is better depends entirely on what the question is. Most questions asked on IRC have absolutely no business on a mailing list, and the ensuing discussions would render the mailing list unusable.
Nobody advocates abandoning email for IRC. Right tool for the job, like anything else in life.
