The introduction this last academic year of the UKMLA should make it more clear which British medical schools are producing the best doctors.
Once this exam produces sufficient data, it will be possible to see how UK med school grads stack up against each other, and may give answers to some of the questions raised on this thread.
IMGs will also be required to take the MLA alongside the current PLAB exam, afaik. This will yield interesting data too, no doubt.