If you are concerned about the health of your hands choose Vim.
I suffered from a bout of RSI in the past, and I found one of the main culprits was "chording" i.e. holding down many keys at the same time. Emacs uses chording extensively whilst VIM uses single letter commands chained in quick succession. This puts much less strain on your hands as the muscles don't have to twist and contort to perform commands in the editor. Injury due to RSI can ruin your productivity so in your calculations be sure to account for this.
