I've gone through writing on Steemit, Busy.org and Steempeak for the most part, and what my brain and body has accustomed the most to, is definitely Steempeak.
When I first started on my Blockchain adventure, I thought Steemit was the only option where you could write your content besides something like a Microsoft Word or even a Google Drive file. That was what I knew back then and I struggled so hard to learn and master the oh so clunky interface of steemit that I even made my sort of own tips and tricks before actually studying a little bit of markdown and HTML formatting.
Then the allmighty, organized and pristine Busy.org came with all of it's features an it took my breath away. I didn't even think twice about switching to busy once I had found about it. The switch was imminent, spectacular and absolutely smooth as butter. The writing on busy was way easier and more fluid than it ever was during my experience on Steemit. Besides, I might have a bias for busy only for the choice of colors they use since blue is one of my all time favorite colors.
Busy's main functions are basically what Steemit doesn't and probably will never do. They don't make you switch between the HTML and the Markdown editors, it just combines them into a single fluid experience. You also got the new and improved drafting of posts where you can literally store any ideas or templates you come up with; I don't even use busy anymore and I've still got templates there because of how useful that function is.
But then, quietly and seamlessly, Steempeak appeared one day on my feed. I said to myself that it was probably worth to try it and voilah, It's the best choice I made for creating content.
I think Steempeak's main goal is to create the most beautiful reading and writing experience the market has to offer. While Busy.org focuses on bringing a lot of new things to the table, Steempeak takes all of that as a given and builds on top of it, making the experience more practical, technical and aesthetically pleasing. It's got the same draft mechanics, editor and image uploading interface as busy but it showcases it in such a different way that it feel completely different but familiar at the same time.
Both have some shortcomings, though. I've spent bad times with Busy where it just forgets to upload my newest draft to the page and this even has caused me to lose some posts on their entirety. Steempeak on their own part don't have this problem (At least it hasn't happened to me) but I do find annoying that it doesn't matter how many times you click on the "Feed" button, it won't update your feed. I've spent hours thinking that some of my friends haven't posted anything at all and then boom I click on the refresh button and I notice that I've lost 4 hours of new content, looking at something that wasn't actually being refreshed.
I think the real answer in here is that people go to Busy over Steemit because it offers so much more, while Steempeak incorporates all of that but shows it in a completely different way. It's a way to look at a much more organized and aesthetically driven Steemit blog. That's why I prefer Steempeak's Interface over any other.