I haven't been to either, but isn't the reason that Budapest Zoo gets a lot of flak that their exhibits for large mammals are mediocre at best and woefully small at worst? Their exhibits for smaller animals seem to be fine. I know that Bern Zoo is praised a lot for having a very high overall exhibit quality and doing some innovative things, but in this case, I'll let the much, much larger collection win. Unless someone can convince me that the difference in exhibit quality is bigger than I thought.