How easy a school is depends alot on the quality of students. For example, professors in Ivy League schools know the students in these schools can handle a high level of work, so they might give these students more work or tougher exams than lets say a professor who teaches a relatively unknown college. Not only that, the competitiveness of students makes it difficult to earn A's because everyone who got accepted into these elite schools got in because they are also achievers in high school. Many courses in Cornell are curved to a B. If the students are equally as smart as you (many smarter and/or work harder), there's only a certain percentage of students who can do significantly better than others and earn A's, while most students will end up earning B's in these courses. In an easy school, courses probably aren't even curved, and the level of work expected is probably significantly lower than the top schools in the country. The difference between an elite school and an easier school is that the elite schools want to challenge students to go beyond what the students are able to achieve in the easier schools. Exams are more challenging, and the average grade for an exam may be a 60, but you get much more out of your learning experience.
by the way, Golfmontpoker, to answer your question, I don't think block system and semester system makes much of a difference. In fact, many dental schools use the block system to organize their curriculum.