I switched from a 7' to an 8' for casting/fishing a jig & cork set up. My normal set-up for jig & cork is using a fixed float and fishing 2'- 6' deep depending on the mood of the fish. Since I'm using a fixed float with this set-up I like the flexibility of the longer rod with being able to fish the jig a lot deeper. With all that said I do feel I get a little more distance.
For getting a longer distance while casting, going to a larger diameter spool can help you get the same or even better results.