TLDR: These are absolutely top of the line notebooks, particularly with fountain pens. In dollars per centimeter of line, the 194 (B5) size is a 14%-20% better value than the 199 (A4) size at current prices ($14.85 for the 199 and $10.04 for the 194).Maurman notebooks are first class. To date they are my favorite of all I have tried. Other top-tier brands I have tried are Rhodia A4 size and Clairfontaine A4 size, which are also excellent, but for a variety of reasons I prefer the Mnemosyne. Fountain pens write like a dream on this coated paper, as do gel pens. The thickness and feel of the paper is amazing. The subdued dotted lines are really nice. The cover is fantastic and the rear cardboard of the 199 or rear plastic of the 194 is substantial. The micro-perforations tear off super smoothly. Also, when you remove the entire page from the notebook before removing the micro-perf scrap, the little nibs stay attached to the page and you don't end up with nibs all over the place. Lastly, the off-white color is classy and archival looking (if you want bright white paper, look elsewhere). Everything about these notebooks is premium. I do wish that they contained more pages. The 199 has 70 sheets (140 sides) and the 194 has 80 sheets (160 sides). Personally, I think that 100 pages would be a better number. But for some reason, all premium notebooks tend to have between 50 and 80 pages. I guess it is a European / Japanese thing.I am currently really geeking-out on fountain pens and paper and have compiled a ridiculous amount of information comparing the different notebooks I like the best. One of the things I have calculated is value for the money. I am not thrilled about how much these quality notebooks cost, so I wanted to know how I could maximize my value. With this in mind, I calculated the number of line-centimeters the 199 and 194 have. Doing the math reveals that based on the current prices of these notebooks, the smaller 194 gives you 14% more value than the larger 199. Of course, this doesn't consider the aesthetics of the size differences. With the 194 you are writing on a smaller piece of paper, will have more "carriage returns" than the 199, and your hand will encounter the side edge and binding edge more often. The 194 is more compact and easier to carry, though. Also, the 194 has plastic on the rear cover instead of cardboard.So, I can't say which format you will prefer, just that in terms of pure value per written word the 194 comes out on top."BUT WAIT," you may say, (well, at least I did), "isn't it likely that with the smaller paper and having to carriage-return more often, there might be some inefficiency involved in coming to edges that may weigh in favor of larger pages where your writing flow isn't broken as often?" To me, this seemed like a likely thing. It seemed somehow intuitive that the more often you had to break to go to the next line, that there would be efficiency losses. So I set out to test this theory, to see if the 194 was truly more cost effective.Well, it turns out, for me at least, my theory was exactly wrong. Not only wrong, but OPPOSITE wrong. When I wrote long lengths of text on both the A4 paper and B5 paper, trying to maintain my exact same writing style, size and spacing, I ended up getting MORE text into the same overall length of line in the smaller notebook. I was shocked. What happened is, as much as I tried to make my writing the same size and spacing in each notebook, my brain didn't let me do it. Somehow, when I was writing on a larger page my writing expanded. And when I wrote on the smaller page it constricted. Looking at the pages side by side it was obvious. Crazy. I honestly thought I was writing the same. So, as it turns out, for ME, the 194 is not 14% more efficient than the 199, but actually 21.6% more efficient (i.e. cost effective). Of course, your mileage may vary. But for me the 194 is a better value.All of that said, I still vacillate between the 194 and the 199. I like the smaller size of the 194 for carrying, and the fact that it has 80 instead of 70 pages. I think I also prefer the plastic back of the 194 over the cardboard of the 199. But if I am being honest I have to admit that I like writing in the 199 more. It just so much more spacious. My ideal notebook would be the 199 with 100 pages. At the same price as the current one, of course.