Neither is 'more serious' - they are both just cautions. IMO it's not for a referee to be considering the implications of whether it's more detrimental for the player/team for them to caution under C2 or C4, it is solely whether they deem the act of kicking the ball away to have been an act of dissent, or whether they deem it to have been to delay the opponents from restarting quickly.The correct LOTG decision is to punish the more serious offence. In the past it made no difference. But now that we have sin bin, sometimes DTROP is the correct decision until there is a law change to say otherwise.