Well I find myself in a unique situation with this question... probably.
My first DS, my first child, had a very rare and potentially fatal blood disorder, neutropenia. He was circ'd because we had NO idea that he had this blood disorder. Had we known we wouldn't have circ'd him because even a tiny little infection could have killed him becuase his immune system was all but nonexistent.
Thing is that same son ended up in the hospital at 7 weeks old with pneumonia. They told us he wouldn't survive because his immune system couldn't handle it. He did survive though. They told us he wouldn't live to see his first birthday because something as simple as strep throat could kill him. He did survive though. After his 1st b'day DH and I met with all his specialists together (4 in total) and they ALL agreed that BF saved DS's life. They said the ONLY immunities he got were from the breastmilk he drank and that it saved him when he had the pnuemonia and kept him healthy enough to survive his first year of life. As it turned out when he hit about 7 or 8 months his white cell counts started very slowly climbing. By the time he was 12 months they were just below what is considered normal (anything over 1200 is normal and his count was at about 900 - 1000).
I also have a child that almost died on formula when we switched her over to it at 9 months. Really really really long story but the short of it is that at this point I consider formula to be "artificial baby POISON" and it will NEVER touch my babies lips.
So if given the choice I would cut and BF... because for my family and my children it could literally be a life and death decision. Circ has it's risks and dangers, and occasionally deaths, but in my case the risk would be considerably LESS than if I chose to FF my child.
Thank God we don't have to chose because I have two intact, BF, co-sleeping sons
mom of 5