Brian and Franz are both on the money. But. Hmmm. How to explain.
I have room in my kitchen and on either of my main boards to use a chef's of just about any length. I have seven front line chef's knives: 12" Sabatier au carbone; 12" Konosuke HD suji (it's not really a chef's but it gets used as one frequently, so... it's a chef's); 11" Konosuke HD gyuto; 10" Sabatier au carbone; 10" Richmond Ultimatum; 8" Ryusen "Blazen" gyuto; and a 7" Sabatier "Nogent" carbon.
- The 12" Sabatier is too heavy to see much use except for tough jobs;
- The 8" and 7" knives are too short, which makes the rocker very pronounced. I hardly ever use them except either to break fish or just to screw around. I especially like the 7" knife for fish and micro-brunoise, like shallots for mignonette;
- The Konosuke is my real go-to gyuto, because they're both so comfortable, light and have such great edge properties and profiles.
- The Konosuke suji gets used as a gyuto almost as often the gyuto*;
- On the other hand, there are some tasks which are a bit much for knives that thin; Fortunately,
- The Ultimatum and the 10" Sab have an awful lot in common. Both are great "do it alls." I'm not really sure which I like better -- the Sab is an old favorite; but
- The the Ultimatum is more practical. I've been using the Ultimatum and nothing else (just about) since buying it in November and find it as good an all around as the Sab; takes abuse better, and holds an edge much better. It doesn't have the same emotional resonance though.
- There are very few chef's knife tasks where it helps (me) to have a smaller rather than longer knife; but plenty which work better with longer knives.
- Longer knives require better skills to use the point as intuitively as short knives. But those are very basic and easy to master skills. Mostly translates as meaning a good grip and a straight wrist;
- The lighter the better, as long as the knife is up to the task; and
- The sharper the better, always.
*Not to get too deep into technicalities and my own knife use, I'm not recommending using a 12" suji as a chef's knife as a generic. In my case, it's partly about using as few knives as possible to prep a given meal -- which is a style thing -- and, to be honest, mostly it's a way of showing off; but since no one else cares, it's showing off to myself. Good thing I'm easily impressed.