For me it goes like "4">B'Day>DIL>>>>>>>>>>>>>>IASF.
She considers "4" and DIL to be her classic because it is her most cohesive albums and they are RnB/soul albums where her voice shines the most. B'Day is maybe better than DIL but some songs like "Me Myself and I" or "The Closer I get to You" "Speechless" **** on it. Sadly their are some letdowns like "That's How you like It"
or the "I'd rather be with U"'s remake that makes B'day the stronger album of the two.