The objective is to exercise and sleep as high as you can
Just one night at Whitney Portal is better than one night in Lone Pine.
Bob has stated it perfectly - but I will make it even stronger.
Lone Pine at about 4,000 ft is a nice place for
after the hike, but
before the hike it will do
nothing for altitude acclimatization.
The official medical definition of where the body experiences significant effects of altitude is 8,000 ft. Based on the Mexico City Olympics and Boeing and Air Force and other data, many believe that figure should be 7,000 ft. To expose your body to enough altitude-effect to begin the acclimatization process, you should sleep that high or higher.
Can people climb Whitney without pre-acclimatization nights? Yes, but the odds of success (and enjoyment) are much better with sleeping higher.
