I carry these: http://www.moleskine.com/catalogue/classic/cahier/cardboard_kraft_cover/set_of_3_squared_cahier_journals__kraft__pocket.php http://www.moleskine.

I carry these: http://www.moleskine.com/catalogue/classic/cahier/cardboard_kraft_cover/set_of_3_squared_cahier_journals__kraft__pocket.php http://www.moleskine.com/catalogue/classic/cahier/cardboard_... The main reasons are that they're thin and fit in my back pocket easy so it goes everywhere, and since I'm always sitting on it, the paged being sewn in prevent it from falling apart. Composition pads are generally bulkier and glued together or spiral bound which is also pocket-unfriendly. I've got other 3x5 notebooks that are bulkier than the Cahier Journals and I just never take them with me. I'd probably avoid sitting on a binder clip too. They also have rounded corners which help prevent the pages from catching on my pocket and getting folded/torn/ugly, and it has a nice inner pocket for receipts or other sources of notes. Superfluous, I know, but I like the cream colored paper better than white paper, and the plain cardboard cover develops a nice patina that other stuff generally doesn't. They're about 3 bucks and only 64 pages each, which is quite steep if you write a lot, but I only go through one maybe every 2 or 3 months, which makes the cost difference negligible to me.