No. Carborundum can operate at higher temperatures and voltages than silicon, but it isn't more efficient; it just lets you run the transistors hotter and at higher voltages, so they can switch more power. The nitride is actually more efficient, but it's more delicate to overvoltage. (I think it also withstands higher temperatures, but in a wallwart the problem isn't that the transistor loses its ability to switch; it's that the plastic case melts.)
You can relive my emotions from when I learned about the astounding properties of nitride transistors (in 02017, I think) in https://dercuano.github.io/notes/jellybeans.html#addtoc_1. Unfortunately there weren't any carborundum parts in my list.
SiC has a lower electron mobility than GaN (and, in fact, even Silicon), so in identical scenarios it can't switch as quickly as GaN chips.
SiC has significantly higher thermal conduction than both Si or GaN, though, which makes it more suitable for cases where you need a ton of thermal capacity (inverters for EVs, for instance).
Both technologies are in their infancy, though. You can get better performance out of either by improving the process technology aspect, so it's hard to say one will ultimately be better than the other. Given the electron mobility though, it seems GaN will ultimately win for devices that aren't thermally limited.
You can relive my emotions from when I learned about the astounding properties of nitride transistors (in 02017, I think) in https://dercuano.github.io/notes/jellybeans.html#addtoc_1. Unfortunately there weren't any carborundum parts in my list.