The ease of use in terms how simple it was get setup up & running our system within 10 mins! I would like more flexibility when creating or editing reports but that's not much hassle anyway as you have access via API if needed - which we do from time too so no problem there (as long at your supplier provides).
We are using delta Xe primarily because they provided us such great support throughout their trial period where some other companies had left things late etc., even though everything worked perfectly well out offor several months before hand!!