I've published some works about twitter user behavior (I attach one of my paper below). Your idea is very interesting especially if you take also others SNs into account. Specifically, I found this article about your question http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4390308/ but it refers only to different regions in the UK.
Bye
Article Comparing Twitter and Facebook user behavior: Privacy and ot...
That's an interesting question and I would have been VERY curious a month ago when I had not started using Twitter seriously. But I see Twitter now as (a) a making connections tool, (b) an incentive to keep me very current in my field, and (c) a way to share links to important information. The length of the message is somewhat secondary to the way it is worded - PLUS you need to consider message without hashtags included because mine are long because I want to reach more people
I've published some works about twitter user behavior (I attach one of my paper below). Your idea is very interesting especially if you take also others SNs into account. Specifically, I found this article about your question http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4390308/ but it refers only to different regions in the UK.
Bye
Article Comparing Twitter and Facebook user behavior: Privacy and ot...
Found a Linkedin pulse article on Social Media trends in 2015. Though this may not answer your question directly , it certainly could be a great way to give you some ideas on ways you could go about researching this topic. This is not a peer reviewed article.