Which ones?

Three of us did the TA with a mix of the previous style waterproof panniers (the ones with the flap over the roll down closure) and the non waterproof ones they called MTB panniers. They held up well on that tour, several other tours, and a lot of commuting. I like them just fine.

I have not tried the latest waterproof ones (the ones without the flap), but given my experience with the older style I wouldn't hesitate giving them a chance.