If we are talking about 6 year courses with an intercalated BSc years i.e. you graduate with a BSc after 3 years and then go onto clinical school, they tend to be at schools without a 5 year option. These courses are likely better since you do get bonus points on your Foundation application for having an intercalated BSc, something you usually still have the option of doing in a 5 year program.
If we are talking about a 6 year course with a foundation year, I have heard that it is easier than a 5 year course, typically the foundation year is for international students who have gone through a different curriculum and the first year catches them up on anything they might have missed.