I'm not saying the situations weren't different,they were.But there is one thing that they have in common,and that is zoro and sanji were both deperate,but one was depicts as still being in control,the other as depressive.
Zoro was in ''control'' because it was about him getting killed if he didn't do anything.
Sanji had to worry about his father figure in the east blue, which was unreachable and his friends the SH's and even Kamabaka island. Sanji didn't had another choice. Ofc Sanji is not gonna smile like an idiot, because everyones lifes were on the line...
You can't compare their attitude in 2 completely different situations...