If you want to move a dedicated flash off the camera, you'll need a special extension cord to do it. These cords are more expensive and harder to find than the simple PC cords for a non-dedicated unit. Perhaps the best reason to own a dedicated flash is its ease of use in fill-flash situations. The higher the guide number, the more powerful the flash. As flashes increase in power, their weight and cost increase, too.
Most flashes use four AA batteries.
Flashes put a heavy strain on batteries, so buy only alkaline types. For even more economy, use rechargeable nicad batteries, and always have an extra set of batteries in your bag. A common problem for all of us is putting the flash away and forgetting to turn it off. By the next day, the batteries will be completely dead. With fresh batteries, a flash typically recycles in six to eight seconds.