As above, very different courses. I'd note that if you want to go into any professional psychologist role (e.g. clinical psychology, forensic psychology, educational psychology etc) you need a BPS accredited degree - so if you did a philosophy degree and wanted to go that route, you'd need to do a master's conversion course.
For anything else though it won't really make much different what subject you study, so in that frame you just need to think about which you find more interesting and enjoy more. Particularly think about the methods of teaching, learning, and assessment - for philosophy I anticipate there would be a lot of reading, with lectures and discussion based classes/seminars/tutorials, and then a lot of assessment by essay and essay based exams. For psychology you would have some of that kind of assessment, but also labs, assessment by problem sheets/data analysis, and likely both "practical" lab based assessments as well as lab write ups, and the exams may have more of a mix of short answer, MCQ, long answer, and data based questions.