In theory the double red cell apheresis, 3x a year, should amount to the same number of red blood cells as a single unit whole blood donation 6x a year. They should be more or less equivalent. I do the double red cell donation because A) it's easier to only go 3x a year instead of 6x a year, and B) walkiing out the door I feel better after the double red cell, because they return my plasma, and they replace the volume of fluid I lost.
That said, you really feel the lost red cells the next time you work out. You'll feel out of shape because of the double hit your oxygen carrying capacity took. But you'll adjust quickly.
My Hct runs in the low 50's. 51, 52, 53. It's never been 54.