I enjoy working with paper. My favorite notebooks are ISO A4 size because they give me a bit more vertical room and still fit well in my backpacks. The issues

I enjoy working with paper. My favorite notebooks are ISO A4 size because they give me a bit more vertical room and still fit well in my backpacks. The issues that come up with regard to US Letter size paper seem to be: 1) It's not metric -- yes that's true, but A4 is 210mm x 297mm. These numbers seem completely arbitrary and don't take advantage of the metric system. I wish the US was on the metric system, but it's not so 8.5 in by 11 inches at least has the advantage that it is measured in simple numbers with respect to standard measures in the US. 2) It's easier to store and work with A4 because it is one half of an A3 sheet -- however, US Letter is one half of the US Tabloid/Ledger size. The ANSI (American National Standards Institute) paper sizes in inches are A (8.5 x 11), B (11 x 17), C (17 x 22), D (22 x 34), etc. and share this advantage with the ISO standard. 3) The aspect ratio is is approximately sqrt(2)/2 for all paper in the A series, the B series, and the C series. But why is having but one shape of paper an advantage? Sometimes it's useful to have choices depending on the content to be printed on the paper. Furthermore, the ANSI paper sizes simply have two aspect ratios alternating as one increases paper size. It is argued that printing posters with corresponding flyers is easier with ISO paper sizes. But this is true with ANSI paper sizes: one would have to jump up two sizes from letter (ANSI A, 8.5 x 11 inches) to ANSI C (17 x 22 inches). So, for the case where one would like to print at ANSI B, the aspect ratio of the page is a bit different. Here we have, what appears to me, to be the first real advantage of ISO over ANSI paper, where we need to print a flyer at A4 and A5 (but not A6). However, this hasn't been a problem for me personally. I'm usually working with pages that have additional constraints. For example space for bindings or differences in margins between recto and verso sides of two sided printing. Whenever there are bindings involved the aspect ratio advantage goes out the window. 4) Every country uses ISO sizes, why not the US (and Canada and Mexico) -- well, this is oversimplifying things a bit. Take a look at the Wikipedia page for paper sizes. There are Japanese variants, German extensions, and Swedish extensions listed that deviate from the ISO standards. There are also Architectural sizes listed that are designed to have simple ratios for their aspect ratios. The idea that we would somehow be better off with fewer choices (just one) really for aspect ratio really strikes me as wrong. I like all the variety available in paper.