I prefer to use the event.preventDefault() most of the time because is more descriptive, and sometimes you have to show your code to your project manager or someone who doesn't understand these abbreviations that are so common between us. In the end, most of the code go through Uglify, and the length of the variable name is not an inconvenient in production.
Same goes for the index vs i. Let's say I just want to use the index as key for my React components, I use it as i, but if I have to do any other operation with it, I will go for a more descriptive name.
Remember that you read as much code as you write, and it has to be as friendly for you as it is for the machine ;)