Why are "Graphical abstracts" advantageous? Although it is optional, many publishers recommend creating a graphical abstract. According to some, this can provide greater exposure of your article:

its use is encouraged as it draws more attention to the online article

Why?

Example of an abstract including graphical abstract, from a recent issue of ACS Synthetic Biology:

Memory and Combinatorial Logic Based on DNA Inversions: Dynamics and Evolutionary Stability
Jesus Fernandez-Rodriguez†, Lei Yang†, Thomas E. Gorochowski†, D. Benjamin Gordon†‡, and Christopher A. Voigt*†‡

Genetic memory can be implemented using enzymes that catalyze DNA inversions, where each orientation corresponds to a “bit”. Here, we use two DNA invertases (FimE and HbiF) that reorient DNA irreversibly between two states with opposite directionality. First, we construct memory that is set by FimE and reset by HbiF. Next, we build a NOT gate where the input promoter drives FimE and in the absence of signal the reverse state is maintained by the constitutive expression of HbiF. The gate requires ∼3 h to turn on and off. The evolutionary stabilities of these circuits are measured by passaging cells while cycling function. The memory switch is stable over 400 h (17 days, 14 state changes); however, the gate breaks after 54 h (&gt;2 days) due to continuous invertase expression. Genome sequencing reveals that the circuit remains intact, but the host strain evolves to reduce invertase expression. This work highlights the need to evaluate the evolutionary robustness and failure modes of circuit designs, especially as more complex multigate circuits are implemented.
I think it may be a substantial advantage. While I've never had the chance to create one, I really like them myself for a number of reasons. 


When searching through volumes of literature, they are much easier for a reader to take in at a glance than a traditional abstract.
They often provide substantially more information about methods and results than can be packed into a traditional abstract.
They are ideal for sharing on social media such as twitter, making it easy for you or others to promote your work.


And after all, a picture is worth 1000 words. Which is more than one gets in some glossy-paper journals these days.