It's true, much of the same information is on Rock Band World. And yet, there are a few key features on rockbandscores that I've used often:
1) Recent Activity - new scores, and improved scores, that I've earned recently, by instrument / source.
2) Score Frequencies - this tells me all sorts of interesting things about how tricky the chart is and if a replay that leads to a small score increase might bump me up the leaderboard significantly.
3) Your Score History - when I improve on a score, I like to see what the previous score was, and when that was first set.
Using these kind of stats to track my improvement (or decay!) in skills is at least 25% of why Rock Band is fun for me.