Try this out.
https://www.youtube.com/watch?v=jcVF3xL_fzkReally gives you an idea of the differences. Interestingly enough, the iridium and copper are near identical ... at least when new. By all measures the iridium will keep the same spark a lot longer. The E3 was surprising to me. My sons S40 has the E3 (previous owner) and it works great. Only comparison I have is on my Yamaha Stratoliner. It's a 2010 and had the original spark plugs with 12k miles on it. I had a lot of random problems with surging at low rpms in 2nd and 3rd gear. After changing them out 4 times and watching the above video, I decided to try the E3's. Made a world of difference in every good way. Now, that probably had to do with the comparison to very old plugs, but I had problems with new NGK Iridium's and new NGK OEM plugs as well. No way do I think they are miracle plugs, but I was very surprised by the engine feedback after comparing all 4. The sound was much deeper, I had more low rpm power, and it was much cooler according to my right thigh.

Gas efficiency also is improved. It's not some massive jump but if the comparison was on a scale from 1 to 10. The other 3 sets were in the 5-7 range. The E3's felt like they were in the 8-10 range.