It depends on what you want to do. Even for simple text processing in one-liners, there are quite a few common tasks that are difficult in awk. A big one for me is capture groups in regular expressions:

    perl -ne 'print $1 if /foo="(.*?)"/' 
    awk '/foo=".*"/ { ??? }'

You can do it with gawk, but it's ugly:

    gawk 'match($0, /foo="(.*?)"/, a) { print a[1] }'

Another is manipulating hexadecimal numbers, which is also a gawk extension.