Headphones-Shure E2 vs E2C

Well after my $%#^#@# cat chewed through my ipod bud headphones I have been using a cheap sony bud set that was laying around the house. I am tired of these and plus they hurt after about an hour. I have done research and have narrowed my search to only Shure. However, the E2C's are noise cancelling while the E2's appear to not be quite as effective at blocking sound. As I am planning on using these at work I need to be aware of what is going on but yet want to use them outside when mowing the lawn, etc. My questions specifically are: How noise blocking are the E2C's? Are they 100%? Is the only difference between these two the noise cancelling feature? Reccomendations would be awesome! Also, I would love to hear from someone who has tried both. Thanks for your time! Scott Burnham, Michigan