They're 2 different songs, in 2 different eras from 2 different approaches. One is acknowledgement and one is mourning. I don't think one is better than the other, and that's with Dear Mama being everywhere. That's really the song that launched 2pac into a new stratosphere, but it also doesn't have the same emotion/pain that you hear in Nas' voice - it has more of a proud standing.
I think favoring either one depends on the relationship that you have with your mother. It's not necessarily which one is better, but which impacts you more.