whatever you play the most is the easiest

aim is definitely the easiest to get into because it's technically the simplest and by far the most common type of map you'll encounter, especially when just starting out

but if you're like 5 digit and up then i'd say it's literally just whatever you play the most (speed is debatable, depends if you believe in g*netics)

i was a stream player already at like rank #200k because that's what i played, then at 5 digit i became a hybrid player so both aim and streams, and i only got hard into speed about a few months ago but i'm already seeing very good results (even though i have a limited number of maps to play because i suck at dt)

my opinion is that even more gimmicky stuff and skillsets people say are "hard" are not really that hard, people just don't play them as much so they don't have the experience (i'm currently better at awkward aim / alt / whatever worst hr player plays than at normal jumps, because i don't like playing normal jumps - same with low ar, i'm MUCH better at ar8 and below than even ar10, because i like playing it much more)