Comparing Mac's and Unix manuals?

Question

How can I list differences between Mac's and Unix manuals?

For example, between the following commands

uniq
guniq

I tried the following unsuccessfully

diff (man uniq) (man guniq)

Answer 1

That should be

diff <(man uniq) <(man guniq)

To answer saua's question from the comments:

Bash turns <(...) into a named pipe, which the diff program sees as a file. So as far as diff knows, it's comparing two files.

Answer 2

Try this:

man uniq > uniq.man
man guniq > guniq.man
diff uniq.man guniq.man