I liked the Premium paper more than the regular C.D. paper. While the C.D. is fairly smooth (a touch smoother than Leuchtturm or Rhodia), the Premium is even smoother, which I prefer. Both papers portrayed ink colors pretty accurately though some of the more subtle chromashades didn’t show up as much as other papers out there. Both had some bleedthrough with flex nibs, so I’d avoid flex or super wet nibs/inks on both of these papers.
At around $4 for 52 pages in the Apica C.D. A6 notebook, I’m ok with how it behaved, though I wish it came in more options than just lined. The Apica Premium C.D. A5 notebook costs $19 for 96 pages, and it’s also available in blank, lined, grid, and dot grid. As I said, both are fine, and I’ll use the ones I have but I probably won’t be rushing to restock them.
(Disclaimer: All notebooks were purchased by me from Vanness Pens (for the A6) and Flax Pen to Paper (for the A5). All pens/inks are my own.)