You can use the full length of the bars for fixing your accessories, which may allow you to carry more on the roof, and thereby get better value from the whole system. Whatever you're carrying on the roof bars is fixed to the aluminium bars via the slots that run full length along the tops of the bars. A frequent problem with the cheaper steel bars is that the roof bar feet get in the way of the accessory fixings.

It's fair to say that if you are carrying a load of bikes on the roof there will be wind noise, but a good set of roof bars will minimise it. Aluminium bars create less drag than steel roof bars and therefore have less of an effect on fuel consumption. This is important, especially if you are likely to use your roof bars frequently or to leave them in place for many weeks at a time. style>