I think the biggest drawback is the extra expense ($150 and up for a macerator pump). Also, is seems unnecessary to run sewage through a blender on its way through the stinky slinky.
When discharging raw sewage overboard in the open ocean, this might make sense (mainly the pumping part, not the blending part), because the head is often below the water line and sewage must be pumped up and out. Also, macerating reduces the chances of solids clogging up the discharge line. However, RV black water is gravity fed and doesn't require pumping.
While a macerator pump can be used, it seems to me to be an unnecessary expense and just something extra to fail and need a stinking repair (literally).
Just my opinion, but "KISS"; and use the $150 for something memorable on your next roadtrip.