And also different programs are calculating different routes with same maps.

iGO Primo Israel, Israel NG, PAL and World calculated different local (city) routes with exact same settings and same (HERE) maps in few specific situations.

Route created with Israel NG seems to me as most logical and optimal, for those situations I tested.
It was not "shorter" but it was using less left-right turns, which is simpler and could save some time.