Ediscovery export much larger than EV archive and journal

Hi,

I'm puzzled by how much larger the exported pst size from DA in comparison with the exported archive from EV. I exported an archive including journal mails from EV which total to about 20.2GB and this contains emails from 2010 the time EV was put in place. Another request (same user) was to export all pst from 01/2011 to 9/2014 and this  came out to a whopping 42.4GB. To be certain, I checked the emails to ensure that I'm only pulling emails coming and sent to this user and they were. Any ideas as to why pst is much larger in DA? Any feedback is appreciated.

FYI, when searching from DA I used 2 parameters: Date Range and To or From email address in my case: first.lastname@company.com.

Thanks!