BBQ purists would argue that you can only really get that true BBQ taste from charcoal as charcoal adds flavour and depth to food, whereas gas simply cooks. Certainly, charcoal imparts a smoky style, which can be enhanced by the addition of wet wood chips or herb branches.
However, whilst charcoal adds flavour, for some lighting charcoal can be a tricky business. For even expert grillers there remains the set-up time; and you can also control the heat by varying the depth of charcoal across the grill from thin/low to thick/hot. The addition of a natural charcoal lighter, such as coconut gels also helps, and you can now even get coconut charcoal.