This is one of those topics that seems to split people. Some say yes, some say no. I've got 'em front and rear and I think they firmed things up a tad.
We had a big debate over this a while ago. Check out this thread;
it should make a difference, but maybe not a huge noticeable one. stainless steel lines never expand during use, where the factory brake lines tend to expand and lose the amount of pressure