The Baby Bottle's character is quite different from the Blueberry. The Blueberry has a very contoured frequency response which makes it sound great on many vocalists (as you've noticed), but it may be too colored for some sources. The Baby Bottle has a much flatter frequency response which makes it a much more versatile microphone in general, but it doesn't quite have that "sheen" that the Blueberry has. If you go to BLUE's website and look at the frequency response charts for each microphone, you'll see why...the Blueberry's chart lookes like a roller coaster, whereas the Baby Bottle is relatively flat with a gentle rolloff at the top and bottom and a small bump near 2K.
The diaphragms aren't quite the same...they're both 6-micron diaphragms, but the Blueberry's is center-terminated and the Baby Bottle's is edge-terminated.