IPL or intense pulsed light and BBL, broad band light are just two different broad band light therapies that are marketed by different manufacturers. The question of which of these two is better for removing brown spots completely side steps the issue of what therapies may actually be at least as effective, less expensive and even quicker in many cases. The use of superficial peeling agents, such as full strength glycolic acid, TCA 15%-25%, and Jessner's solutions, particularly the latter two, all have a very long (going back decades) history of tried and true use for treating blotchy, irregularly pigmented skin and solar lentigines (sun/age-related) brown spots. Relatively expensive, bells and whistles supposedly "next best thing to come along" are not necessarily either the most cost effective, quickest or least expensive way to treat these kinds of unwanted spots. You would do well to seek consultation with a board certified aesthetic physician in order to more fully discuss all options available, rather than jump to the industry-supported marketing hype that surrounds so much of the new light and energy-based devices out there. Best of luck to you.