Hey,
I would likely take UC Davis predominantly because you can get started right away with the program and not worry about paying anything out of pocket. UC Davis is a good option.
However, I completely understand potentially taking the year masters at Chicago/LSE. Honestly, it really depends on how much you care about rankings over just hitting the Ph.D. straight on. Judging by your account name, however, it looks like choosing UC Davis might be a better option.
Thank you so much for your insightful reply! I really appreciate it and will take your advice to heart as I begin my application process in the coming fall. The whole process can be daunting, so it is really nice to hear from others on best practices for setting one's self up to be in the best position possible. Thank you again!