That's so funny that you are between those 2 specialties! I thought I was the only one! When I started my 3rd year, my first rotation was OBGyn and I LOVED it! I don't know if it was because it set the standard, but I had a really good time. Nothing could even compare to it until I did my EM month. Then I was stuck. I loved continuity of care, but I loved the acuity and diversity of EM. What it boiled down to for me was specifically identifying what I liked about each specialty. For OBGyn, it turned out that I liked the pelvic/speculum exams and ultrasounds, mildly liked vaginal deliveries, and was completely ambivalent toward the surgeries and c-sections. I also knew if I went into OB, I would specialize in either urogyn or MFM, which would have been a total of 7 (or 8) years in training. When I realized that I could do my favorite things (pelvics and ultrasounds) in the ED AND see a wide variety of patient complaints (which you lack in OB), then the decision became clear. Yes, I would have to give up direct continuity of care, but I found that the frequent fliers provided me with all the continuity I could stand! Oh, and I was shaving 3-4 years off of my total training (depending on whether I matched in a 3 or 4 year EM program) which equals doctor's pay sooner! Of note, I remember hearing that if you could love OBGyn as a rotation, then you should do it, because not many love it. PLEASE don't listen to that advice! Just because you love something, I would definitely keep looking because you may find that you love something else MORE (as was the case for me). So basically, with all of that said, I say sit down and really look at what you like about each specialty. You will find at least one more personal pro for one of them and that is what you will choose. Good luck!
-P.S. I'm officially DONE interviewing for EM!!!! WOO HOO!!!!!!!!! And I certified my ROL this morning!!! Match Day, here I come!!!! (fuzzy navel anyone?)