It might be hard to find comparisons because people tend to go one way or the other. I have the 22" Kacey BD and the 39" DO. I wanted *something* in the 27" range for studio and location work, and I opted for the 27" DO. I like the versatility as it comes with a white deflector, inner and outer diffusers, and the different combinations offer different looks. Plus, I love the portability. I would guess that the setti with deflector and baby DO with deflector only will look different. Question is, how important is this difference to you? If you put a sock on the BD and diffusers on the DO, the light will probably start looking more similar.
Cameras: 1DX, 1D4, 20D, 10D, S90, G2
Lenses: Canon 10-22mm, 16-35mm f2.8L II, 24-70mm f2.8L, 70-200mm f2.8L IS, 300mm f2.8L IS, 200mm f2L IS, 50mm f1.4, 50mm f1.2L, 85mm f1.2L, 1.4x TC, 2x TC, 500D macro, Zeiss 21mm
Lighting: 580EX, Elinchrom 600 RX's, D-Lite 4's, ABR800, 74" Eli Octa, 100cm/70cm DOs, Photoflex Medium Octa and reflectors, PW's, Lastolite Hilite, Newton Di400CR bracket