I use a Moleskin Cahier notebook slipped into a Yellow Birch Outfitters PocKit Pro to keep it from getting destroyed. I like the Cahier notebooks because they have perforated pages that I can tear out and leave notes stuck to places with glue dots.

If you’re just looking for the most durable notebook though, something like the Rite In The Rain spiral bound notebooks would work. Just my opinion but for pocketability’s sake I would advise against a hard case since it’ll be bulky and won’t conform to the curves of your body.

Rite in the Rain 3x5 is my edc and I really enjoy them. I’d recommend buying one without a case and see how it works for you and if you really need a case for it you can buy one from their site.

I carry a Field Notes (or similar cheap) notebook around with me. They work great for my own use at work and at home.

I’ve used Moleskine and Clarefontaine but truthfully these days, I just carry a piece of regular photocopy paper folded into 8ths so I can write down random stuff. Anything important on it later gets typed into a computer or photographed on my phone.