too many reasons to even begin to list.
essentially, though, with stocks, you can judge individual issues on their own strengths and weaknesses. much more opportunity. and you can be long and short at the same time in different issues. you can trade different sectors. you can trade "pairs" you can use derivatives (yes with futures too, but few do). fundamentals come into play. relative strength, volume, news, earnings, a million factors. you can trade listed or otc., you can watch price action and size. the list of reasons is endless.
it is not about just guessing (or "anticipating" if you like the word better) the direction of the market.
then again, what do i know? i don't trade futures. or i haven't in a very very long time. i will occasionally trade etf's, which seem to be similar to trading futures. never got really enamored with them. maybe it is just all really about personal preference, and there is no right or wrong. or better or worse. just different strokes.

rs7