A nut driver set like this:
http://buy1.snapon.com/catalog/item...5&group_ID=744&store=snapon-store&dir=catalog
For my application, I exchange different size 1/4'' sockets on my spinner handle, just like switch bits on my ratchet screwdrivers.
So what is the advantage of using single nut drive? exactly same reason as multi-tool screwdriver vs single screwdriver?
I use nut drivers for those jobs where fasteners are installed with low torque and often do not have a phillips or flat head as a second means of removal. (As mentioned above, the hollow shafts are extremely useful as solve several problems if you face that type if dilemma often.)
Those most often for me include car dash fasteners, underdash and firewall fastneners, engine bay components , small and large appliances, electronics, small gasoline engines like lawnmowers, weed wackers and motorcycles as well as bicycles. Anywhere the nut is torqued only to hand tight they are quick and useful in my life.
Unless used daily and very very very very often, I feel the SO is a high price to pay for most who have a need for nutdrivers. Even more cost efficient instead of buying individual driver sets is buy a ratcheting screwdriver, a 1/4" hex to 1/4" sq. drive adapdtor, use 1/4" sockets and be done. Plus you get the beneift of the magnetic tip to hold the nuts that most nut drivers do not have. Even cheaper is a std. bit holder with the adaptor.
For $330 for SO Metric and Std. sets, I could find a LOT of different ways to get both hollow shaft nut driver sets AND a ****-tonne of other tools with setting foot on the "truck".
On the other hand, if you have money to burn or are shitting rolls of quarters like some Federal Reserve Bank mutant goose, by all means get both Snappy sets. They do get used once you have them no matter the brand.