Why can't I AAA?

[rauchster]

Why can't I AAA the easy songs is what I want to know.
I played Seattle's Finest recently to knock down my average rank. I got 2 goods on it. Took me five tries. Out of 169 notes. In an incredibly easy song considering what I normally play.

And yet, On harder songs I get these big strings of perfects.
20031023 (9, Challenging) - String of ~230 perfects.
Devotion and Desire (8, Very Difficult) - String of ~270 perfects
Visions (NRGyzd mix) (8, Very Difficult) - String of ~280 perfects, and including a couple very tough (for me) patterns

Since I can hit strings of 50-100-150 perfects regularly on songs 6-7-8 bars of difficulty, why can't I hit 100-150-200 on songs waaaay easier?

On my first try of Seattle's Finest I got a good on the first note, and the second.
Second try I got a good on the third note.
Third try I got a good around 15.

Yet, I pull up {Blaze} or Victims and Martyrs or Megane De Ne! and hit the first 75-100 perfect on the first second AND third tries.

I'm just confused why I'm getting good at FC's, and yet suck at my AAA's.