Haven’t read enough Lovecraft but I think McCarthy does a better job at inducing visceral reactions with only as much language as needed; every word has its place, every sentence its own work of art—whereas I believe Lovecraft deliberately used archaic spellings of words to add an air of antiquity to his writing. McCarthy might also surpass Lovecraft in painting immersive, open‐spaced, bleak atmospheres with his prose (reinforced by intensive and accurate geographical and even botanical research), which adds to the horror—although, again, I should withhold my verdict until I read more Lovecraft.
Also, I could be wrong about this but apparently a majority of Lovecraft’s works were small‐scale horrors and ghost/alien stories; people seem to inflate the pervasiveness of explicit cosmic horror within his bibliography.