Actually I chose to learn dialect first because literally everyone who knows anything about the language cautions that native speakers will swear up and down that you should learn MSA and then be completely incomprehensible to you because of how little anyone actually uses it in the Arab world.
I've been working with my teacher for a year and a half now and she agrees that MSA is basically pointless unless you intend to start consuming arabic language news or listening to arabic language political speeches.
BTW this is from a professional cultural expert who's literal job is to prep government workers and businessfolks to be able to engage successfully with the Arabic world, something she's been doing for 20 years now, so I'm pretty sure she knows what she's talking about.