I'd go with the larger one but that hard plastic case you linked is extremely bulky, I had a similar one on my iphone and I hated it. If you're going to jailbreak it, go into cydia and get something called "glovepod." It turns the volume buttons into next/previous and it makes the sleep button pause/play. This is at the lockscreen after you hit the home button to unlock it. You'll see what I mean when you play with it a bit.