Depends on fit and what sort of conditions it will be travelling. Warwick rack bags are crap..just avoid. I've got a Gator 2U one which is pretty good, but its only done car travel/light use. SKB plastic rack cases always seem very pricey and aren't that durable, but could do the job fine if you are always shifting it, and its not bounced around or chucked too much.
The one you linked to looks ok to me, but don't expect it to be very tough.