In the end, I definitely feel the large Cahier is the best one for me.
I think the best way to explain it is that the Cahier is like the
Macbook, and the hardbound Moleskine is like the Macbook Pro. I prefer
the Cahier for the same reason I prefer the Macbook over the MBP, even
though I do appreciate the virtues of the more serious and classic
alternative.
The Macbook has no latch, and it is easier to just start using
whenever a thought or whim strikes you. You just open it and start
working. There is a latch you have to press a button to open on the
Macbook Pro. This puts a slight speedbump between you and getting down
to using the MBP.
Likewise, the Cahier is easier to open up and start using. It is also
easier to flip through and browse. It is lighter and easier to throw
into your bag or wherever. By contrast, to write in a hardbound
Moleskine, you have to pull off the elastic band. It's also a bit less
convenient to browse, owing to the hard covers, which prevents
flipping through the pages like you can with a softcover-bound
booklet.
I don't much like the medium size Cahier because it doesn't stay open
like the large one, and its pages are too small to flip through like a
magazine, as you can with the large one. I like the large one in
black.
Anyway, that's my personal opinion and experience. Different people
will naturally have different preferences and needs. Cheers,