Dust Proof feature in a waterproof camera - does it matter?

I'm trying to decide between the Nikon AW100 and Panasonic DMC TS4 waterproof cameras. The specs are very close but the only notable difference is that the Panasonic is Dust Proof. I have no idea how much this matters? It's $50 more then Nikon… Is it worth the extra money? Thanks.

Added (1). To address below: I was wondering if it was a gimmick because of the "waterproof" as well. Probably not to bring in a dessert, but yes for the beach and mountains (skiing).

Yeah it does matter just in case you go any where, where there could be a lot of dust and just in case your not going to use it for a while, dust won't affect it!

Sounds like a marketing gimmick to me. If a camera is waterproof it's airtight. And if it's airtight dust won't be able to get it anyways. Were you planning to take pics in the desert or someplace with lots of dust? If not I don't think it'll matter.

If you have ever had dust get into your lens or on your sensor, you would know