Monday-Sunday. I like to keep the weekend together, it just seems "right" to me, haha.
(I also order my day planners in Mon-Sun format)
I just finished 2018 (first time finishing a year! Never got past a month or 2 before!) and will likely use the same or at least similar template in 2019. I made my own super simple template with a 4X12 journaling "spot" and filled the rest with 3X4, then added layers so I could easily swap out 2 portrait for a landscape, 4 portrait for a big portrait, smaller journaling & extra photo/s for the larger journaling depending on photos/stories/kit for that week.
My plan for 2019 is to work on PL pages one week out of each month. In 2018, I had finished 10 pages and started 7 more between January and October. Then got crazy and did the other 35 pages (+ added papers & embellishments to the unfinished 7) between October 25 and Jan 2. I'd prefer not to do it that way again