I just spent 8 days testing 6 different pleated filters. I tested them on 2 different airflow settings. 3 electrostatic, 3 weren't. MERV ranged from 6 to 11. I also tested them new and after spending 24 and 48 hours with the fan running constantly. I didn't directly test pressure drop but instead tested the amps on my ECM blower which is designed to keep constant airflow. What I found:
(1) Higher MERV didn't necessarily mean greater pressure drop.
(2) Electrostatic didn't necessarily mean greater pressure drop
(3) Electrostatic invariably loaded up quicker
So the moral seems to be change your elecrostatic frequently if you use them. Also, most allergins are fairly large particles, compared to smoke for example, so a higher MERV may not give you greater allergy relief and they cost a lot more. Also, if you are allergic to dust mites, humidity control may be more important.