Twitter co-founder Evan Williams took a few shots at Instagram and Facebook when asked by Fortune about Instagram surpassing Twitter in number of users.
While I think he brings up a valuable point about Facebook inflating it's number of users, and the value of a ton of users compared to a smaller count of very engaged users, he kind of loses his way in his second paragraph when he says,
First of all, I don't agree that Instagram is at all any shallower than Twitter. Both serve their purpose and you see art and dreck on both sites. It seems rather false to say that just because a government or world leader (or their PR team) have figured out how to use Twitter and not Instagram that makes it better.
Granted, Twitter does conversations across disparate groups and people pretty darn well. Especially in a way that is quick, fairly easy to find and easy (almost too easy) to join. Twitter's speed is it's primary advantage.
Instagram is pretty quick too, but you aren't as limited in your caption and replies to posts are buried underneath the comparatively large images. I think one of the things that people, both popular and not, like about the platform is that it lets the poster set the tone. Their photo appears, then the caption and then all the rest of it is just "errata". Likes and the most recent comments appear, but the posters message is the first thing.
Compare this to Twitter where, depending on when I jump on I may see someone's reply first before circling back around to catch up the conversation so far. It is also, and I think this even more importan: it is impossible for someone else to post a URL or link to another Instagram post. All of that kind of discussion happens, of course, on Twitter.
So Instagram has one advantage for marketing that Twitter doesn't, a certain amount of control on the part of the poster to set the discussion/say their piece with fewer distractions.
If I was an advertiser, I think I'd prefer to see my sponsored posts appear on Instagram, rather than Twitter. And because both platforms are predicated on selling advertising as their primary revenue, Instagram wins.
Does anyone think Kraft cares about deep discussions about racism? I don't think so. And it's hard to sell trips to Disney between Shaun King's tweets.
Clearly there is room in the world for both. But investors want Twitter to be not just big, but Facebook-big. It's not going to be that way with "in depth discussions". If Instagram is going to become Fox, Twitter will be NPR. That's fine, but the value proposition (and means of revenue) is quite different.