A big issue with these things is that a lot of people get low-cost ring-lights that are really just a bunch of LEDs. Some of them are so dim they don't even publish their guide number, or the guide number isn't anything close to the amount of light from a real flash. If you're hoping to do macro shots, then you'll need a lot of light to allow small apertures that give you more DOF, and you want to use real flash with a pretty high guide number.
|Nowhere by Nanard 92|
from The Illusion of Depth and Distance
|Green Tomato by lim yau tong|
from Growing Fruit