I started out with a pannier and used it happily for several years. But every once in awhile I would hit a pothole or have to hop a curb and it would fall off. One of those times, the s-hook got caught in my spokes in traffic and I almost went down. I switched to a backpack and have been using it for about a year with success. I only carry clothes and a book, not too heavy. Check out Vaude, they are awesome.