Given that AIC was the band that got me into rock/metal in general, I am kind of biased towards them. Still, I find AIC's music to be more relatable, and I connect with their music on a deep level. They've gotten me through many a tough time, and Layne's words make me feel like I'm not alone (there's a Staind song about that
).
Nirvana is also an incredible band though. Kurt is one of my favorite lyricists of all time. That man was creative. But in my mind, they can't compete with AIC.