Comm is a UNIX utility used to compare two sorted files line by line
Grep is a command-line text-search utility originally written for Unix
"I rather prefer grep since it s much faster than comm and also does not require the input to be sorted"
from question "Show lines in unsorted file1 that do not exist in file2"
"If this is an issue you could try sd stream diff which doesn t require sorting like comm does nor process substitution like the above examples is orders or magnitude faster than grep -f and supports infinite streams"
from question "How can you diff two pipelines in Bash?"