I liked that the Columbia program was more flexible - only one required course, no time limit on completion (Bren is a full-time 2 year commitment) and you can easily cross register at different schools (law school, business school, architecture, SIPA, etc). Every alum/student I reached out to enjoyed the program. I also liked how diverse the student body and teachers are (actual professors and a lot of adjunct professors who are practitioners in the field...lots of networking opportunities). UCSB was super appealing to me, the faculty there is amazing. The program seemed more strong in conservation and ecology and I am more interested in the business and policy aspects, which Columbia is stronger in. Also Bren has 8 required courses so the pro is you get really close to your cohort, the con is that it's not as flexible a curriculum and I already had a similar very liberal arts, interdisciplinary undergraduate experience. Additionally the Bren program didn't seem as diverse... seemed like most people are from California/west coast and younger like everyone's in their 20s. Between the two, Bren is def the better choice if you think you want to stay in academia. It's a great program and students move on to do PhDs afterwards.
Let me know if you have more questions! I definitely was torn between which to choose and talked to a ton of students/alums from both programs.