Regular Wonder Woman isn't all that close except speedwise
Buuhan > Buutenks > Buucolo > Super Buu > Kid Buu >= Pure Evil Buu > Fat Buu
That's how I always saw it.
(And his transformation rules still don't make any sense^^)
Fat Buu seems to be a little stronger than Kid Buu. Mr. Buu is a different story since he became explicitly weaker after separating from Evil Buu. Even then, he still put up a better fight against Kid Buu than he did against Evil Buu. Also, Goku freaked in the manga over Big Buu/Western Kaioshin-absorbed Kid Buu for a second because of his power level, then he calmed down once it went back down as he reverted to Kid Buu. So, it's:
Buuhan > Buutenks > Buucolo > Super Buu > Big Buu > Fat Buu > Evil Buu > Kid Buu > Mr.Buu
Ichigo: What even *are* you?!
Kenpachi: Some say my mother was a train. Some say that I'm a rejected Godzilla monster too strong for the series canon. But everyone says: I'M THE KEEEEENPACHIIIIII!!!!
Yeah, I pretty much agree with this.
Majiin/Fat Buu isn't "normally" as powerful as Kid Buu because of the opposite personalities. He just sits there and takes attacks and almost never does nothing or plays around, Kid Buu immediately blows everything up and fights with full potential. However, when Fat Buu gets mad and shows his eyes, he's actually drawing from the higher power source that he has and is approaching Super Buu level. Which is also something Goku never saw, making his assumptions about Fat Buu fit in.
That was filler though. In the manga there isn't any fight at all, Evil Buu just turns him into chocolate at the get go.Even then, he still put up a better fight against Kid Buu than he did against Evil Buu.
And Kid Buu somewhat toyed with Fat Buu.