I think this story will make my point.
I was on a FM rotation and my preceptor was trying to convince me to switch from OB to FM. He continued to to state that with a FM residency, you can do all OB or all DERM, or tailor your practice to do whatever you wanted to focus on. I then asked him if he knew any FM doctors, that did only Derm, his response....."No, it isnt practical to do all derm".
Moral of the story....if you love OB, then do OBGYN, the reasoning being, you ll get the long and boring cases, but every time there is even the slightest problem, you will be passing it off to an OBGYN.