Which quest are you talking about?
If it's the one that starts the quests chains, you can get both by getting the second option before completing the first option.
If you talk about the end quest where you upgrade the cape you have, there are three possible endings and you have to select which you want, upgrade one or the capes or talk to another NPC to get more exp and fame.
From what I saw, the capes are the same.
More info at: http://strategywiki.org/wiki/MapleSt...s/Nihal_Desert