Dark Souls Vs. Battletoads

For a long time, Battletoads was regarded as the most difficult (with about being cheap) game ever made.  I have written before on my experiences trying to best that game. But some time ago, Dark Souls was released. And it started kicking gamer's butts immediately. It was made to kick your butt, with real penalties to dying that incentivize learning how not to get killed. I haven't played far into it, but I got a real good idea of how much Dark Souls relishes killing me. So which is harder?