Popular Content with statistics module incorrect
There are many reasons the counts from different web counters are off (I had a former boss drive me nuts with that back in 1998 ...):


statistics module increments page counts on every reload
when a page is cached it might not increase the statistics counter, depending on the caching used. GA does increase because it's based on browser page loads
GA doesn't increase when bots are visiting your site (because they don't execute javascript)


I usually rely on GA for my business reports and just use statistics to show counts for my users. 

You could also use the Google Analytics module to import GA numbers back into Drupal.