Celluar optics really win in the thermal area. They can dump the heat many many times faster than a monolithic blank. In larger sizes (perhaps 25" and up?) they start to make sense from a mass perspective.

Where cellular optics lose big is in cost and lead time. It seems that no one wants to pay even close to the cost of what it takes to make a good cellular mirror. To the best of my knowledge there is no commercial company that has a proven track record of delivering apertures over ~12" in a reasonable time frame.