Backflips are extremely easy, but you can make them look super impressive.  It's just having the balls to commit, they truly are easier than 3s.  But who wants to see a 3, everyone can 3.  Backflips look better.
As for Backflips Vs 7s, it depends on how well you do it.  If it's hucked and mad penciled then no, if it's sick with a grab then yes, although some people would still be more impressed by the backflip haha.