One friend of a daughter went to Chicago. He was a very strong student. He used this phrase when he came over for a visit over Christmas/New Year’s break.
MIT and Caltech are at the same level of demanding as Chicago. If you are going to attend a university on the “Caltech, Chicago, MIT” level then you need to be ready to work very hard without a break, and the desire to do this needs to come from inside the student. If you are not driven to do this, then it becomes a very long and very tough four years.
I do not know if “more relaxed” would describe my experience at Stanford (for my master’s degree). There is a lot of homework and the classes go fast. I did find it more relaxed compared to MIT. However, I do not know how much of this was because it was a shorter program, and how much of this was because I was driven to do it. By the time that I got to my master’s degree I wanted to do it, I was ready to do it, and the desire to do it did come from inside me.
I think that if a student is considering attending a highly ranked pressure cooker type of university, they need to ask themself how strongly they feel that they want to do it. It is certainly possible to attend a slightly lower ranked university for a bachelor’s degree and then go on to a highly ranked graduate program (whether for a PhD or for some other graduate degree). It also is not quite just ranking. For example I used to know a couple of people who got their bachelor’s at MIT and a graduate degree at Harvard. They both have said that Harvard was easier (of course “easier than MIT” is sort of like “shorter than Kareem Abdul-Jabbar”).
It is important for a student to look for a university that is a good fit for them. It can be hard to know what a good fit will be. To me at least this seems quite a bit more difficult to figure out compared to just looking at university rankings.