GPA vs Undergrad prestige and difficulty Consider the following scenario:

Bob goes to a top-tier university for his undergraduate degree. This university is known for its extra challenging curriculum and Bob also challenges himself while attending. Bob is able to learn the material, but due to the extra rigor of the college, Bob graduates with a 2.5 GPA (B/C Student).

John goes to a different university for the exact same undergraduate degree as Bob. His university has a significantly easier curriculum and as a result, John is able to graduate with a 3.5 GPA (A/B Student). 

Other than going to a different undergraduate university and their GPA, Bob and John are identical. Both are now applying to the same grad school and the same program at that school. Which is a better graduate school candidate?

Note: I know this question is similiar to How are GPAs from different universities evaluated for admissions to MS programs in the USA?, but I am looking for an answer that is narrower. In my case, I would like to know how two candidates would be judged if there only differences was undergraduate GPA and undergraduate university. In all other aspects of the application process, these two hypothetical candidates are identical.
Admissions don't come down to a single number or any single factor. Knowing no more it is impossible to say which of these two is a better candidate. 

While it is true that some universities are considered "better" than others, it is an ephemeral thing. Some marvelous teachers work at some quite "modest" places. Moreover, the universities that have a really great reputation, often do so because they are able to offer more learning support to undergraduates, though that isn't always the case. They can often attract top faculty, of course, for financial reasons, but that doesn't necessarily translate to better undergraduate learning. Certainly not for every student. 

Someone with a low GP from a top university, might have been somewhat disconnected from the learning process and had little contact with those top professors. Someone from a lower ranked place might have that higher GPA because he/she worked closely with the faculty and has a much better grasp overall. This, too isn't necessarily true, but it can happen. 

Another factor, of course, is that not all of the "top" students go to the "top" schools. Money plays too big a part of who gets to go to, say, Harvard. Some people just go to a local State University of modest reputation due to family or other reasons. But they can get an excellent education there, and have done. 

And don't assume that John had an easier path or that his university had a "significantly easier curriculum". There is no basis for saying that. Some graduates of highly ranked places are also quite weak in skills. 

However, I suspect that there is a general feeling among academics that a student who has done well locally (high GPA) has taken advantage of the offerings and is well prepared, while one who has not done so well in the local environment may not be as well qualified to continue. But that "general feeling" needs additional evidence, so isn't considered definitive. 

Admissions is a game of balancing. Many factors are looked at, grade point and college reputation among them. But those alone won't tell a useful story about a candidate.