Should I get the 13 inch or the 15 inch macbook pro?

My uncle said I should go for the 13 inch and buy a monitor for the extra screen size.

I'd love to spend your money, but I have to agree with your Uncle. For the longest time when I used my 13" MBP Retina I wished I had the 15", but after plugging in a 24" Dell monitor, that wish went away!

Either way you go, you might want to consider the largest SSD drive you can afford and max out the RAM to 16GB which the 15", I believe, comes standard with.

17" laptops are not out of question in schools now, but so are iPhone SE's.

If you need horsepower get the 15" and if someone has an issue with it don't make it yours.

If you are worried your classmates will object to your screen size go with something smaller and slower and less expensive.

My preference is the 15" for the power, especially if editing video, coding, playing games, ... I especially think the 15" screen is the better option if you will be spending a lot of time using the computer for class assignments.

For how long do you expect to use the laptop (barring accidents, losses & such)? Given that these are sealed systems that cannot be upgraded, expanded or such, you should consider what you will need at the end of its expected lifetime, where assignments, projects and such will impose bigger requirements.

If money is available, I'd go for the top-end 15" that comes maxed out with RAM. The speedier CPU and big SSDs are overkill, especially at Apple prices. But you will get twin GPUs that will provide excellent graphics performance and permit not only games but much faster results from high end graphics and animation programs.

I would say the 15" is to be preferred.

I would choose the 15".