I am a surg onc fellow and I love it. Huge cases, lots of collaboration with medical oncology & radiation oncology. You get exposure to such a wide variety of cases, major HPB, breast, melanoma, upper GI, lower GI, thoracic, H&N, etc.
The applicaiton process was competitive, and I think research, letters, etc are the most important part. I didn't take dedicated time off from residency but did some research at MSK on post-call days, etc and got a nice paper out of it.
I think the big programs and only "first tier" programs are MSK and MDA. They are clearly superior to the other programs in terms of research, reputation, etc. They are also EXTREMELY competitive and I think a lot comes down to who you know. For example, I know someone who took 2 years in research, nature publication, excellent resident with the best credentials and didn't even get an interview at MSK.
I think the rest of the programs are all very good, the SSO only gives fellowship status to a limited number of high-quality programs, so the overall fellowship quality is excellent no matter where you go. I am at a "2nd tier" type program and I'll give you a brief run down on my experience from interviews. Note, this is highly biased, entirely subjective, and just based on limited experience and may in fact change from year to year.
MSK, MDA- highly selective, outstading training. Only possible downfall is perhaps limited experience as the surgeon, instead you will be 1st assist.
City of hope- very nice, tons of OR volume, very good laparoscopy (largest robotic rectal series out there). Lots of hours, not very cush but will come out with outstading training. Stand alone program with no residents
Ohio- among the best, very busy lots of volume not much MIS. Probably the best program for autonomy, they want to make sure they don't have to teach you to operate. Very dynamic faculty highly respected.
Fox Chase- huge in laparoscopy (lap major livers, HPB, robotic rectal/APR/TME, etc) get lots of H&N and thoracic (maybe too much if you don't want to do it in practice), Most cases are done directly with attending so probably middle of road in terms of autonomy. Stand-alone cancer center with no residents
Chicago- very well respected program big research center 3 year program with 1.5 clinical 1.5 research. Posner is boss and he is very well known. Good training
Moffitt- highly liked during interview trail, I didn't interview here
Toronto- very nice if you like Canada. They can adapt training according to your wishes, for example can make 2nd year a colorectal fellowship (HUGE!). Big HPB program but they have their own HPB fellowship. Lots of interaction/shared cases with residents
Roswell Park- part of the initial 3 programs in surg onc (MSK, MDA, Roswell) very good place, lots of research available. Dedicated center with minimal resident interaction.
Brigham/Dana Farber- among the worst programs for surg onc (excellent hospital of course) fellowship bad because residents are very strong, too much competition from residents for cases and you will as the fellow get 2nd dibs. Powerhouse for research/resources so may be the right place for someone who likes the research.
Hopkins- similar to Dana Farber, fellowship seems like 2nd class citizen
John Wayne- Santa Monica!! Huge melanoma (Morton) and breast program (Giuliano). Home of the sentinel node. Spread out across LA for colorectal, etc. Competitive place, and I liked it very much.
Virginia- smaller program and not as competitive on the trail
Providence (Roger Williams)- small program and not as competitive on the trail but Espat is great liver surgeon. Very dynamic guy exciting to be around I think you will get outstanding HPB here
Pittsburgh- Probably the best place in the SSO for HPB. They have several different tracks according to your interest- research, MIS, HPB... extremely competitive work very hard get very nice training. Also big HIPEC center.
Miami- smaller program, not much MIS but big proportion of very advanced disease huge cases. Lots of residents around to help with service but I didn't get the feeling they had much competition.
I am sure I'm probably forgetting a couple but these were my immediate thoughts. You need to get your own opinion and judge for yourself. Each place has different feel, strengths/weaknesses. For example- no residents means no competition for cases (good), but if chest tube needs to be put in at 3am you are the one to go in and do it (bad). Several of the stand-alone centers have NO ER!! How great is that! (MDA, MSK, Fox Chase, City of Hope, Moffitt)
Good luck!