I believe the case used by Bike Friday is a hardshell with some kind of clamp, rather than zippers. It seems like that would make in less likely to take in water. Some zippers are made to be water proof or water resistant, but I would expect most of them to take in some water in a heavy rain. But then I haven't tried it yet. When shopping for luggage, almost every case I looked at that had a zipper had at least one review complaining that the zipper had failed when the bag was loaded up. It seemed like for durability, a zipper was not the preferred closing method if you were carrying any weight. That said, I went with a zipper because it was cheaper, and I just hope it's strong enough. It certainly held up on the first trip.

If money were no object, I'd go with a stronger closing method that's less likely to leak, but that doesn't mean that a zipper is a bad way to go. If I waited until I could afford the best possible set up, I'd still be waiting for that first trip. I think finding something affordable that works is a good way to go, and keeping it priced lower than Bike Friday's system should make it a very attractive deal.