My experience has been that Defender's prices are usually lower than West Marine's, although not always. In some cases however, Defender's prices have been significantly lower. A few years ago, I bought a replacement tiller at Defender; the price was $69. The exact same tiller was $119 at West.
A couple of years ago I bought a new Lowrance chartplotter/fishfinder at the Defender spring sale. The price was $100 less than the same unit at West Marine, and about $70 less than on Amazon.
The sale prices on Cetol or bottom paint are usually no better than West Marine's prices; in fact, I've found that West Marine usually has the best bottom paint prices if you hit their spring sales just right. There's also usually a manufacturer's rep for PFDs, and they are well-priced (although not a jaw-dropping steal).
And for stuff like line or marine hardware, Defender's prices, while always competative, are not worth an interstate trip.
For me, one of the biggest attractions is that it's an EVENT; a place to go, and thing to do to help drag me out of winter and start thinking about spring commissioning.