If you like your test cases in Ruby (or maybe .net) and are willing to

dig through "hard to understand" documentation - then Watir is a tool

for you.(if you are perl/php/java shop - don't even bother considering Watir

for now)

Watir does have advantage that its recorder uses IE to record.

With Selenium - if your site does not work with Firefox - you will

have to manually write the code(not big deal)..

But the biggest advantage of Selenium is its support for FIT HTML

and the vast languages/browsers/platform that it supports.

(with good documentation)

But maybe things may change in future.