Neither, make it so I'm actually achieving something instead, not an arbitrary "WELL DONE U DUN DID EZ MODE HAF GAEMSCURR +15 EPEENZ". World of Warcraft does it good, for example doing every event achievement (takes about a year to do) gets you a pink proto-drake flying mount. Xbox kinda does it, some achievements give you a gay little outfit for your avatar, it's a shame I don't give a fuck.