Pros and cons??
They’re completely different kinds of program and institution.
Cass is part of City University in London, and offers undergraduate degrees. It has quite high academic requirements, asking domestic students for three A grades at A level, and Americans for three AP scores of 5.
Bournemouth & Poole College is a Further Education College, for ages 16-19 - something like a cross between high school, a community college, and a trade school. You can use it as a gateway to higher education, as they have an access course for people without suitable qualifications for university entrance, but it isn’t degree level itself.
What are your academic background and stats?
Cass is very selective and located in a thriving, very epensive city.
Bournemouth is a nice resort town, not a metropolis, and B&P College should be very low-cost, offering qualifications that could help you skip a year of university, sort of like a community college.
("“high school + trade school + community college” is a great description).