I think its unfair to imply that IPL is a light bulbs, that's really scaremongering.
I have both treatments of Laser and IPL in my salon.
To the OP, the wavelengths are different frequencies, and the side affects for both have pros and cons. They BOTH work essentially, granted they wont be suitable for everyone, but that can easily be determined by a number of factors with includes, skin typing, medical history, hormonal imbalances. Even if you had they right skin type, you will still not be able to treat white, red or the blonde hairs due to it being ineffective. The both classified as permanent hair reduction and the only method for permanent hair removal is electrolysis which will treat any hair colour and any skin type.
Also if anyone is unsure please look at the technical spec, as it gives the boundary of where it is in on the spectrum of light- it will show the wavelengths (nm) that it reaches the energy output (j-cm2) and the pulse length (nm) these are in essence the most important variable factors when choosing a machine. hths xoxo