Well, sorry if I havent't expressed myself well enough. I also meant this as an outside observer, asking myself why this other way was not taken into consideration.
I mean by this that had I, been a member of the Fellowhip (The Might the Almighty
) I would have thought about it twice before entering Moria.
As for the second part, I think this is a subjective view. While you believe that Moria was, although dangerous, still better then south near Isengard, I think otherwise.
Indeed the marching Haradrim would have been a problem, but you must keep in mind, they were marching all the way to the north, so maybe only by going through the north they could have avoided this at all, but as it was close to Barad-dur that road would in the end be more dangerous. That way the Haradrim would be a problem no matter if the Fellowship had gone through Moria and the north or near Isengard and then south of Orodruin. Indeed, the north was watched by the Rangers and they could have helped the Fellowship, which does give north a certain advantage, I agree. But the south would be less watched, since most of the forces were already concentrated in the north of Mordor.
All in all, I don't wish to speculate how the Fellowship would have gotten into Mordor from the south, just as I don't wish to speculate how they would have done that from the north, had things gone otherwise during the Quest.