So, what I mean is that like a golf club, with a knife you are moving your hand, and the handle, and using the blade to cut. Like with a golf club, the longer the tool, the more exact you have to be with the angles you are using. If your hand is angled a little, off, the end of the blade is going to be further off. On the other hand, a longer blade is proportionally longer, so if you are slicing green onions, you are using the rear middle of your blade, and you can cut more onions at a time if that section which is efficient for cutting green onions is longer. Standard is between 8 and 10 inches, and anything in there is OK. The depth of your countertops also matters. A longer knife isn't doing you a lot of good if its tip is embedded in the wall. One other point of advice is to be wary of a lot of these knife forums. The people there know a lot about knives, but often little about cooking or cutting food, so they treat the knife less as a tool and more as the end. That's fine as far as it goes, but it also leads to a lot of people with expensive knives and bad technique because they are developing an internet groupthink way of cutting so that they can utilize a knife that is deemed the best.* Kind of like men's clothing. *to expand on this a little, knives and food styles are linked by culture, and the techniques to create these foods influence and are influenced by the tools used. It so happens that a gyuto knife is really a good substitute for a chef's knife, but using Japanese/Asian knife techniques tends to make life difficult in cutting the ingredients that make up western cuisine. When you combine the love for Japanese knives and the desire to sharpen them to a narrow angle and high polish, you end up with a tool unsuitable for western cooking in lots of ways, which is why if you go on and read some knife forums they are going on about push cutting everything, which works well with polished blades and doesn't ruin super thin ones, but is a ridiculous way to go about cutting most of the things that are necessary in the food of the west. The converse is also, of course, true.