I own both cameras and you're right that having XLR-ports is nice, but the 7D's codec with 48Mbit is MUCH better than EX3's 35Mbit. Downside is that you gotta convert the 7D's mpg4 to something better suited for editing DNxHD on Avid, Prores on FinalCutPro or Cineform. (The rolling shutter and aliasing problems of the 7D have nothing to do with the codec, by the way.)
As to your question regarding DOF. If you're wide-open f 1.9 on EX3's stock-lens and on the tele-end of the zoom, you can get quite nice and shallow DOF, but as soon as you zoom out a little bit everything is sharp from here to nebraska. The size of the EX3's chip is nowhere near as big as the 7D's and the DOF gets very deep quickly on wider lenses.