From the webpage:
Top 5 reasons to use ack
Blazing fast
It’s fast because it only searches the stuff it makes sense to search.Better search
Searches entire trees by default while ignoring Subversion, Git and other VCS directories and other files that aren’t your source code.Designed for code search
Where grep is a general text search tool, ack is especially for the programmer searching source code. Common tasks take fewer keystrokes.Highly portable
ack is pure Perl, so it easily runs on a Windows installation Perl (like Strawberry Perl) without modifications.Free and open
Ack costs nothing. It’s 100% free and open source under Artistic License v2.0.
I was doubtful until I saw the documentation page.
I had to concede that there were almost enough command line switches to qualify for a man page. 😉
I suspect it is going to be a matter of personal preference.
See what your personal preference says.