I think there are some misunderstandings about Cedars-Sinai. I know I had some, until I got there.
It's a 900 bed hospital -- 900 beds! -- with the new ICU tower that someone mentioned above. There's no way a residency program can watch that many patients. So, there are many, many private physicians that work there, who have no interaction with the residents.
The teaching service is uninsured or Medi-Cal patients mostly. The teaching faculty is dedicated faculty that round with the residents, attend in clinics, etc. Residents there engage in research, have many publications, and are just as "academic" (whatever that means) as any other university-based hospital. There's journal club, senior grand rounds, etc.
Cedars-Sinai also has a huge transplant program -- the teaching service cares for all liver transplant candidates and post-OLT patients. There is a separate ward team for heme-onc patients who are mostly stem cell transplant patients.
Another large patient population there are patients with HIV/AIDS. They see a lot of PCP, CMV, toxo, and every other opportunistic infection out there.
They see *sick* patients, and they get comfortable managing complex issues. That said, they get a lot of bread and butter medicine (CHF, COPD, chest pain, etc), because it's a community-based hospital.
In my opinion, it's the best of both worlds.
Fellowships are not a problem, if you put the time in to make a name for yourself. LIke anywhere you go -- how much research you do, publications, etc, are going to get you the interviews for fellowships. You're going to be disappointed if you think you can sit around doing nothing for 3 years and match at the #1 Cardiology Fellowship.
Ultimately, it comes down to where are you going to be happy. Interview at both places and see what vibe you get from them. You're going to spent a LOT of time working, so make sure you like the people you're going to be working with! Good luck.