Snapchat is fun and all, but Instagram is better. Well, in my eyes, Instagram is better for a few reasons, and I quickly deleted the face-filter app that took up just shy of 1 GB of space on my iPhone because I felt Instagram's version of stories had the greater potential. One of the largest reasons I see more potential in Instagram Stories over Snapchat is the virality and reach my Story can have. Today, Instagram announced they will be adding people's public stories to the Explore page, which will essentially let them be seen by more people. If you have not caught on, this means there's more potential for my stuff to go viral.
Some of the reasons I find Instagram to be better include that I am seeing far better engagement, even on sub-accounts with small followings. I'm also able to upload full-size photos and videos to the story within 24 hours of taking the photo, so I technically don't have to be in the moment to share content immediately, and it shows on the full screen compared to adding a strange white border. Those aren't huge selling points, but damn are they nice for someone wanting to share content on social media today.
Those aside, one of the biggest reasons I find Instagram growing past Snapchat in the form of a better overall experience is the possibility of going viral. With the higher rate of engagement and larger user base, adding public stories to the Explore page will help people find my work (and yours) much faster.
If you have yet to adopt the newest feature and are still searching to find reason behind, it I can tell you that it has become a fun and interesting way to engage with your audience in a way that's separate from the professional level of photos on the main page. Showing behind-the-scenes shots, videos, or even future posts for people to vote on via direct messaging are only some of the things that can help your Stories build purpose.