To clarify/specify a little bit - For the average male 5'10" - 6'2", there is a certain radius that feels right from the hand down near the board at full contact to the hand and arm as high as can be "comfortable" with just the tip on the board. It's not that you can't get your hand higher off the board, or closer to the board, but there is a comfort zone that you want to be in. Most of us prefer a gyuto that at least allows for some precision work with the tip (I like to mince garlic with mine, particularly), and you need at least a small flatish space near the tip to do this. Then, within the framework of that average male size, you need approximately 125-145 mm from the tip down the length of the edge in order to allow for the proper rock, so that the knife can be used to rock when needed, but also so that the knife can be used for slicing with the tip on the board and the knife angled up from the board at just the right angle as to be comfortable and still work (this is probably the second or third most used motion that I use when cutting, btw). Once you incorporate that correct curvature to that part of the blade, it only allows for a certain length of flat real estate to work with back to the heel. On a 240 that translates out to about 100-120 mm or just at 4-4.75 inches or so, ideally, and on a 270 that translates to 130-150 or 5.25-6 inches or so. Most pros (and most home cooks like me of average size who like to chop to julienne) will tell you that that extra inch of dead flat makes chopping a much easier process, from onion to leafy herb to potato to squash, etc., etc. It's one of the reasons why I think 270s are really popular on the boards, and maybe not so popular for the general population, as your average internet user who gets into knives, sharpening, and extended discussion with people he doesn't usually know personally is probably most likely to be a male of average height, while your average knife purchaser (at least in the States) who DOESN'T get too much into sharpening and especially not into going on forums to talk about it is probably a female of smaller stature that leads to needing a smaller knife... ergo people on the forums TEND to suggest and prefer 270s while the average population tends to buy 210s-240s.