I've never trusted any of these driver updating programs, they make claims similar to all the other "PC Booster" tools that it will speed up your PC, make it more stable and more secure. In fact, many of the companies that sell driver scanning software also make stuff like registry 'boosters'.
I'd only ever download a driver from the manufacturer of the machine/motherboard/part and failing that the manufacturer of the chipset the device features e.g. Realtek. And for older hardware without drivers for Windows 7/8, Vista drivers usually work fine.
You've got to wonder, if a driver isn't available through one of these sources above, where does the one that the driver scanner installs come from?