Hey guys! Need your help. I'm looking at these Etymotic Research 6i earbuds... they're $149 I think, and the E4c by Shure are twice as much! What's so different about the E4c? I know they're special fit and everything but the ER6i has the same cone-shape. I've heard good things about both. I'm looking for an earbud which is good for travel on buses especially.