I've been using Mossery planners for a few years now, testing different formats out. I find half-year great because I have lots of options for carrying around: bring 1 whole year, or only the half-year refill without a cover, or half-year + notebook in the cover. The vertical format works for me because I get to see what times are locked in with meetings or appointments. It also helps in setting realistic amount of tasks per day.
The paper holds ink well IMO. I use Muji gel pens (no ghosting) and fountain pens, Sailor Shikiori ink (some ghosting).