I've built a number of wheels before and well as renovating used wheels and I've gained an appreciation of what makes a good spoke key. I've been using the SW-7 standard park tool spoke key for a number of years and then I discovered the SW-20. The SW-7 is great for general purpose but there is a point within wheel building where the nipple gets tight on the spoke as the tension increases and that extra leverage and control is required. This is where the SW-20 is brilliant, although it is only one size (0 on the SW-7) its very comfortable in the fingers when making adjustments. Recommended.
The SW-10 tool is more about turning stuck nipples without destroying them. I've only use it on one spoke which seemed to work. There is a wheel at spindles which is waiting for the treatment, I'll let you know how it goes.