Using jk vs. jj for ESC Remapping in Vim by Steve Losh

Some people prefer using jj instead of jk, but I prefer jk for two reasons: jk is typed with two separate keys, so you can “roll” your fingers instead of using the same one twice, and pressing jk in normal mode out of habit will move down and then up, leaving you exactly where you started, whereas hitting jj in normal mode will move you to a different place in your file.