Both considerably simplify Google Analytics usage with WordPress. You don’t have to open any WordPress file and physically enter the Analytics code. This is especially important if you change your WordPress theme every once a while – or may be upgrade to a later version of a theme.
I personally prefer the one from Semiologic because it ignores your hits if you are logged in as a author, editor or the admin. Without this feature, I was getting too many false hits on
'/?p=XX&preview=true' every time I wrote a new post using Save and Continue Editing feature of WordPress.