Incrementing in C++ – When to use x++ or ++x?

It’s not a question of preference, but of logic.

x++ increments the value of variable x after processing the current statement.

++x increments the value of variable x before processing the current statement.

So just decide on the logic you write.

x += ++i will increment i and add i+1 to x.
x += i++ will add i to x, then increment i.