Some carbon steels can be finicky and reactive with onions and citrus, to the point of turning cut surfaces brown or black and making a mess, even with a patina - for that reason, it's good to also have a nice stainless blade on hand.
Keeping that in mind, I like to have a good stainless 'laser' gyuto in a smaller size, good for aforementioned alliums and citrus, and everything, really - Misono UX10 210mm is my choice here. It's whippy and fast, and can get sharp, and has scalpel-like profile.
For carbon, they are my workhorses on everything else, so I don't mind a thicker knife with a slightly wider grind and some heft, because they're going through root veg, meat, and more. I use 240mm gyutos for this purpose.