Earlier, Kotaku did a PS Vita size comparison to show not only the machine's size, but also the memory card's and the game card's size. In this video, my nimble fingers stick tiny cards in slots and then pull them out. Fascinating!
That's incredibly poor design. If you buy physical games, it'll be a bitch to swap them out—something you'll probably do many, many times. If you buy downloadable games, you'll be swapping out storage cards, many many times. Either way, I think Nintendo wins the usability round—what with the easy-access came cart slot on the top. No tiny hands or nails required.
Both having a thin, snap-in (read: will be broken first) flaps covering each slot is piss-poor design.