Ranked in these QuestionsQuestion Ranking
Pro Easily reachable with both hands
In most keyboard layouts it is the biggest key and is reachable with both hands easily.
Pro No need to move your hands away from home row
Pro By default, <Space> does the same thing as lowercase `L`
Con There are better uses for <space>
It is better to use space for EasyMotion. This is an important key that's rarely used.
Con Space is commonly used to toggle folds
For those who use folds a lot, a common mapping is:
nnoremap <space> za
Not a problem if you don't share your editing session with anyone else of course.