Unlike residency, fellowship is 12 months to obtain a very specific skill set. For cardiac, that includes certain cases, complexity of those cases, skill of the surgeons involved, etc.
Next, factor in the name recognition of some places, and the smaller sample size of the Cardiac Anesthesia world, and you will realize that certain names can carry much weight to practically any job in the country. These people meet up with each other at conferences, and are often just a phone call away when you are being investigated as a potential partner in a group.
Point is, when I was applying to fellowships, I had a dream list of 5 or so, an acceptable list of another 5-10, but beyond that I would have forgone fellowship entirely. So I disagree with the statement that 80% of cardiac fellowships will give you equal training, even though I do believe that is (mostly) true for residency. It's s different ball game.
And Penn was on my dream list, but I didn't end up there.