<p>According to this, Turkish is <em>somewhat</em> easier to learn than Arabic. This is for native English speakers though. You said Turkish would be your 3rd language, I’m assuming English is still your first.
[Wikibooks:Language</a> Learning Difficulty for English Speakers - Wikibooks, open books for an open world](<a href=“http://en.wikibooks.org/wiki/Wikibooks:Language_Learning_Difficulty_for_English_Speakers]Wikibooks:Language”>Wikibooks:Language Learning Difficulty for English Speakers - Wikibooks, open books for an open world)</p>
<p>That being said, I personally think Arabic would be more useful/marketable. You bring up a good point at the end, not a lot of colleges offer Turkish. If you have your heart set on it, then go for it. If you’re simply looking for a unique third language, I’d choose something more useful, but that’s just me.</p>