So I'm debating my next DLC purchase and stuck between Thieves Guild and Dark Brotherhood (maybe one day down the line I'll get both, but since I'm a filthy casual right now, I'm only going with one). Both are attractive to me because they offer skill lines. So for those that have played both, which skill line do you think is better and more useful for long-term game play? I primarily focus on PvE and soloing content.