I'm not sure how much of a difference it makes now adays with the advances in technology (rod building materials, braided line), but a longer rod is viewed as being able to cast further based upon pyhsics. I know that some people can cast just as far with an 8ft rod as others with a 10 ft or bigger rod and vice versa, but you also run into "backbone" issues. A bigger rod is stronger, thus it can handle more weight in the cast, but also gives better leverage to turn a fish when it runs or to keep its head up out of the rocks. A good example is at the breachways. Sure you could use an 8 ft "noodle rod" and get fish in, but after it takes you an hour to get one in and everyone else is ready to cut your line cause you're holdin everyone else up, you'll see that you just don't have the leverage to get the fish in cause there is so much bend in the rod. In order to have the same leverage with an 8 ft rod, you'd need a pool cue and that is not ideal/versatile for when you need to reach the outer bar with a bomber or an eel cause it will cast like a pool cue.
As far as fishing the sand beaches, you can get away a lot more with an 8ft rod depending upon the weight you are castin cause you don't need to turn fish. No obstacles. Down the cape the advantage of a longer rod is it keeps the line out of the crest of the waves more due to the angle between the rod tip and the distance out to your lure (once again geometry/ physics). This will have less of a dragging effect on your lure (not getting pushed into the beach as fast; less drag).
Man, I think I have just burned my brain out with all this technical talk.
I use ten footers cause that's what I was always brought up usin' since I was a little kid. Old habits die hard.........and I feel more powerful holding a bigger rod.