Making ALL DISTRICTS more competitive allows those who live in those districts to have a larger voice in what happens.  Politicians actually are forced to listen to their constituents.  A prime example is Mike Coffman's district which used to be gerrymandered and controlled by the far right.  Tom Tancredo is a result of that district not being competitive.  Now that it is competitive Mike has had to listen to and represent everyone in the district - including Hispanics and immigrants that now make a large portion of his constituency.  I think that has made him a better politician (he is obviously politically shrewd to) even if I don't often agree with his stance.