As far as I know and am ready to be corrected again here lol pushmode forces the command directly to the server wheres newchanban adds it to the bots list and then dumps the command in the server queue. It would therefore depend on how much data is in the queue, but pushmode is inherently faster.
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If the automobile had followed the same development cycle as the computer, a Rolls-Royce today would cost £100, get a million miles to the gallon, and explode once every few weeks, killing everyone inside.