ESS wont warranty the rest of your car if their supercharger blows up. Dinan does. How much does peace of mind cost you?
Peak Horsepower: 451 @ 6000 rpm
Peak Torque: 439 lb/ft @ 4500 rpm
Dinan is also 30 more HP than the ESS, and I believe ESS is in Europe which might hinder any kind of customer service issues.