I prefer the apostrophe-s version myself. I defer to the Chicago Manual of Style and Strunk and White’s Elements of Style on this account. I was mostly taught and quizzed on AP Style in college (as I took many journalism courses and worked at the paper), and that style guide used the bare apostrophe. AP Style also taught me not to use the Oxford comma. As much as I blindly followed AP for many years, in the years since, I’ve found myself on the side of the Chicago Manual of Style for apostrophe-s after singular names and the Oxford comma in lists.