Ok so I am a fourth year MS, going into OBGYN, lemme try to answer these questions to the best of my ability and based on where I am from and where I have interviewed thus far for residency.
1. Wild Pathology and cool OB cases are pretty much the norm if you go to any major academic institution, specifically, places that provide free care or accept a wide variety of payment options. The location of the hospital is also a major determinant of this. A bigger city is more likely to see a wide variety of things more often, whereas community and private practices are a little more low-key and may send their more troublesome, high risk cases to the bigger, more experienced hospitals, specifically if the delivery will require that baby spend some time in a tertiary care NICU. Now, OB in a sense is pretty un-predictable no matter where you practice which is why the field is so great. Although only certain institutions may deal with extremely high risk pregnancies such as those patients with substance abuse, or comorbidities such as HIV, you can never predict who will post partum hemmorage or go into preterm labor or PPROM.
2. Loving gyn onc is what many people love about this field. But, you need to keep in mind that 4 years of your life will be dedicated to OB and GYN and all that this entails. from what i have been shown, you can rotate thru onc at the very least 1x per year (alot start in intern year) which is alot of experience for a sub specialty. Now, my suggestion is that if you like the rest of the field, then it is worth it, however, you should try to also rotate on your gen surg rotation with the gen surg onc docs, because you should figure out if its the surgical ONC you like or specifically the field of gyn onc- there is a big difference. Also, to see if you like and could handle the OB side of residency, try doing an MFM sub-I in your 4th year, and see what u think... its busy as hell, and all OB- if you cant stand 4 weeks, u cant hack the residency
As far as competitive goes,for gyn onc, yeah it is competitive, but if you are good (which you should be if you want to do this) then you will be fine. I am a true believer that wherever you go for residency, its all in what you make of it, and if you want something bad enuf, you will get it.
3. politics and life. So this is what I am understanding is the whole point of the residency interview process and the match. I have been told that if you let the match work, it really does. The point is to find the people and the program u match best with... i have faith in the process. You are going to come across politics wherever u go, so I am not sure what to say about that except you can ask the residents when you interview at the programs, and they will be honest.
4. From my understanding, yes, doing gyn onc means never delivering another baby. I love the obstetrics aspect of OBGYN and it was the first thing that drew me to the field. But I do have an interest in REI, and the majority of these docs never deliver another baby again. So my plan is to go to a residency program that gives me as much experience in every aspect of the field as possible so that I can make the right choice for my subspecialty. If you are a true gyn onc doc, you will be OK with never delivering another baby again... and there is no doubt that you will get plenty of chances to do that in residency, every program delivers 1000's per year. Overall, the truth of the matter is, you will never know truly what field you belong in until you get a good amount of experience in it.
In response to your thoughts about the primary care and clinic aspect of it: So one of the things that I love about OBGYN is that you get the exciting nature of the hospital setting, but you have the intimate setting of continuity of care in the clinics. Even if you plan to be a surgeon, (gyn onc included) you have to do clinic- these people (and their loved ones) are scared and have medical problems - and in what you are interested in- cancer. They need the support of clinic to know that they are comfortable with their surgeon and they trust this person with their lives. Some people feel the need to follow-up with their oncologist for the rest of their lives even if the oncologist feels the patient has been in remission long enough that they could stop seeing them. In OBGYN, no offense but its womens health, and women live off of ever-changing hormones, and counseling is at the very least half of the practice. It can be really good, don't rule it out just yet! Also, as I am sure you know, primary care is a dying breed at this day and age. Doctors care about their patients, not just if they fit into the specialty that they provide. I plan to take advantage of this intimate relationship that I will form with my patients and use it to support preventative medicine, (i.e. if the patient is 50 y/o and presenting with endometrial cancer... has she had a bone scan or colonoscopy? lemme make sure and at the very least, set it up for her.)
I hope this helped. Have a happy thanksgiving and don't worry, you will find the field of medicine that matches your heart and mind- i know that I did