In the computerised Flight Planning programmes which I've written, unless an adverse wind gradient exists, for short flights, the programme seeks the Level where the Climb Profile intersects with the Descent Profile.
The chosen cruise level, then, is the next lowest hemispherical level to keep ATC happy, or that giving 2 minutes minimum cruise time, to keep the crews happy.
In short - The 'user friendly' slingshot manoeuvre.
Regards,
Old Smokey