Barmy I am curious why you say this. Is it common knowledge Yale immunologyis really great or can I find rankings for this kind of stuff somewhere? I always see people mention "x field is great at x school" but I find it very difficult to gauge this kind of stuff just from reading department webpages. In my field I kind of know who are the hot shots just because of papers I read/conferences/water cooler talk/etc., but how do you gauge this for other fields? If there's a resource for finding out what depts are best at what places then that would be super helpful to know.
P.S. just so I don't hijack your thread completely, I think you should go to one of the MSTPs if you're serious about the PhD training and cannot see your future without a significant research component. Otherwise go Yale MD. I do not think the money should be your primary incentive, because ask yourself will it be "worth it" to suffer 4-5 years in a lab doing stuff you do not want to do? I see the money as a bonus or extra perk, rather than an incentive to pursue MD/PhD training. Just my $0.02