Actually, they don't since they both clear into C. They clear in exactly the same way. Just depends upon where one is on the list. (Once things get to airport control in foreign airports, though, all bets are off with regard to clearing order.)
Thanks for clarifying what I meant. They're in a different position on the upgrade pecking order, even though they use the same fare bucket. Then again, only EXP's have expanded C availability. It's worth a call to the EXP desk.