It's really hard to say, considering that practically everything recorded about him seems to have been filtered through Paul at some stage. You can take a stab at it with the help of some pretty sophisticated textual analysis methods (I think the Jesus Seminar did a pretty good, though not unimpeachable, job of this), but ultimately an analysis always depends as much on readers' preconceptions as it does on the actual text. Kind of like trying to get an handle on Socrates' ideas when all we've got to base them on is Plato and a handful of contemporary commentaries -- except worse, since analogous commentaries don't exist in this case.

I'd lean toward "dissident rabbi" based on the charitable version of my reading of the New Testament, but readings of the New Testament are notoriously idiosyncratic for the same reasons.

You can see my edit for further justification. Paul took up the mantle of leadership and effectively made the religion, but that doesn't mean that Jesus wasn't a cult leader.