Sanguine I know it doesn't speak much of techniques, but if you mapped all of the scored penalties in world cup shootouts, I'd venture they are in the majority in the same areas. But send the keeper the wrong way and it goes in.
Point I am making is that even for those above (Pearce's an obvious exception, he just wellied it), most probably did choose a side and go for it.
Consistent practice should enable a professional player to consistently put the ball right into the corner of their choice with pace making it as difficult as possible for any keeper to save it even if he does get the right side.
Back in 1990 Lineker used to practice penalties and scored two v Cameroon. Story behind that is he used to practice putting them all to one side in training and apparently the day before the Cameroon game the word went up there was a Cameroon scout in the stands watching so Lineker deliberately hit all his penalties to his less favoured side and hey presto the next day when England get the first penalty, he somehow managed to send the keeper the wrong way.