I don't agree with the above post re: Cards. It really depends what you're interested in...
Though Michigan's put up a huge cardiovascular center and is recruiting more new faculty (especially basic science faculty to steer translational research), Wash U's imaging is hands-down cream of the crop. Michigan, in comparison, is an infant in Cards MRI/CT. They are actually sending fellows to other places to train in imaging, so they can get the expertise their program does not provide. Wash U's cath lab is also much more productive; the volume is amongst the top in the country. I would say that Michigan's EP is a little better (especially ablations), but only because EP as an independent branch of Cards really started at Michigan. Stereotaxis and device therapy are better at Wash U. Michigan's heart failure faculty is more productive, partly because there are more of them...but Wash U's clinical experience is more diverse and collaborative (i.e. you can double in imaging and EP or CHF and EP much easier). Michigan has an open Cards ICU (i.e. multiple orders from multiple attendings; multiple housestaff to supervise), Wash U has a closed Cards ICU.
I think both programs are top notch and will provide you excellent training. I haven't even touched on the residency aspect, which is probably even more equivalent than the Cards experience. It all depends on what type of living you want: city or college campus. St. Louis is totally underrated; it's full of CHEAP fun things to do and great CHEAP restaurants. Yes, it's laden with crime in some parts, but those areas are totally avoidable. Ann Arbor is also underrated; it's safe and full of social options affiliated (or not) with the university. It is rather EXPENSIVE though.
If I had to choose between the two for residency, I'd pick Wash U, just because of the wealth of research opportunities (and grant money) the program provides and the diverse patient population that does not exist in Ann Arbor. But it's a completely personal choice; best of luck, you'll be fine with either of them 😀