That is the Question!
I wanted to try both versions of the bum covers to learn and feel the differences. First, bias tape is FAR easier than it sounds like. The bum covers without the bias tape, I felt, are more difficult. I think mainly because my OCD wanted the elastic sections to be perfect. The reality is, they won't be. If you read down through Dana's tutorial...even she admits they won't be perfect. I had a hard time leaving them less than perfect, but when it was all said and done...they turned out KOOOOOT (as Steph would say)!
The girly ones are for 0-3 mos and the insanely cute owls are for a boy 6-12 mos.