In the normal one (not the oversized one) while at the parks I carry my KTTW, ID, credit card, insurance card, and usually some cash. So 4 plus the room for cash, easy. More cards for the cruise since you won't need the cash onboard.
The problem with even the DVC lanyards given at the port or on board is that the plastic is flimsy and the metal ring is weak. If you get it caught on something it can break and tear off. DH lost his and DS's DLR APs that way when it hooked on the restraint. And even though it was Disney product vs a Disney ride and Disney CMs couldn't find it, thy still made us pay for the replacements. (
Disneyland policy)
And the ziptop closure on the various Disney lanyard pouches I've had always always eventually breaks. Both the ziplock style and the Hefty brand slider style ones. And that's not even mentioning the flimsy ring.
That's why I got the Witz. The ring is super sturdy and you can put it in the lanyard of your choice (i like my Ravenclaw lanyard personally).
The waterproof part isn't important when you only have plastic cards in it, of course.