Yes, diff can be useful, and on Windows, you can use Winmerge, a public domain utility to compare files (there are most probably others). But these utilities require the files to be sorted in the same order, which might not be the case. And if you have to start sorting each file before comparing them, then a simple Perl one-liner might do the job faster.
At my work, we are using daily all kinds of combinations of Unix "power tools", including pipes and redirections to connect diff, sort, wc, cat, grep, find, cut, sed, awk, etc. commands, but Perl offers very often a better, simpler and faster way to do things.
And when I have to work on VMS or on Windows, where you don't have sed, cut or awk, Perl shows its superiority even more blatantly.