I've tested both and decided on V6. Obviously the V8 is more powerful, but the torque curve on the V6 is flatter and you get max torque earlier. I wasn't looking for power 'cause when I feel the need I drive my Porsche. THe SRX is strictly our family truckster.
I also thought the 3.6 V6 was fine for the SRX when I took a test drive. However, I was the only one in the unloaded vehicle. Maybe if it was loaded up with people and cargo, it would be a different story.