Why Moria?

[Morsul the Dark]

Why go through Moria?

As I recall both Aragorn and Gandalf either feared or hated the place...It may be because it was the only way....but was it?

I was listening to the Hobbit and it occured to me Gandalf coulve taken the secret passage(the one Gollum used to live in. It says the orcs left the passages alone for a great while so wouldnt it be safe to say it was abandonned? and also afterwards if he was still alive they could have stayed with beo0rn for a bit to get themselves rested...I understand this route wouldn't have been as adventurous but if Tolkien was indeed writing basicly freestyle how far ahead did he think, what I mean is when He was writing the Mines of Moria bit was He already thinking about Lothlorien?

Personally I would have went through the passage if I were Tolkien. But that just be my opinion. I mean I love the way iot is right now but is it possible they could have gone the other way?