For standard integer types, i++ and ++i are identical .
In C++, where you can use ++ on "complex" data types, there is a slight difference in efficiency between x++ and ++x (giving the latter a small advantage), which means that some people use ++x. The main reason for this is that x++ require that you FIRST make a copy of the value, then increment it. The object itself doesn't have to be very big before this overhead of copying the object becomes noticable.
 Of course, this only applies if the x++ or ++x is "standalone" - if it's used inside an array index, or some such, there is of course a difference in that the ++x will FIRST increment the value, then be used as an index, whilst x++ will first be used as an index, THEN update the value.