This is a neat article detailing the difference and similarieties between Moleskine and Field Notebooks. Essentially Field notebooks are more portable but Moleskine offers more options both in size and construction. This article detailed a few different kinds of Moleskine notebooks I was unaware of.
Passion journals to detail what you are interested in from dining out, tea, books, beer, home life and more.
Japanese Inspired Sketch Album where the page stretches out about 5 times it’s original width
One that links up to Evernote (I knew about this one)
Upon looking further the only differences between the passion journals is the cover, also there is no method of expansion. If you are looking for something that accomplishes this purpose but expands check out levenger: http://www.levenger.com/Circa-Simply-Irresistible-Sampling-Kit-5961.aspx
I quickly followed this article with another:
Arguing that a notebook can be much faster and more convenient for learning/jotting down notes on the go letting fleeting thoughts be captured but not capture you. This author even recommends a certain kind of pen for their ability to resist leaking and to write everywhere.
A useful follow up to the previous notebook article, this author recommends the Field Notebooks for his on the go jotting.