My understanding was that responsive was generally a better option too as it reduces maintenance issues (you only change once) and is more shareable as you don't know what device the next person will view the site on.
Of course, I can't remember any recent articles where this has been backed up so I'm no good to you really!
I too build responsively... one site to rule them all. I've not seen statistics as such as to why, but from all the talks/articles I've consumed on the matter it just makes the most sense to me to do it that way.
Of course there are many different ways to build responsively... but I guess they, along with wether you go for a mobile specific or responsive site in the first place, are dictated by the projects needs.
I think you also have to think about budget... we're all trying to make money at the end of the day and I know I can build a responsive site a lot quicker than it would take me to build a mobile & a desktop specific version.