1. I´m for all two (I do facing out variation too, but as a additional stretch, when I need in my workout another vertical pull excercise).
Hands facing out will be my first choice, but hands facing in is great variation of excercise: I feel that biceps head is worked more in this variation and I could engage lover back muscles around spine more in this variation (and some muscles are worked less). At the other hands, hands facing out variation is more comfortable position and it´s one of main traditional stretches with strands.
However, I don´t do ODP - front variation so much (and if I do it, it´s hands facing in variation).
2. I like back press more and perform it oftenly, although I do both of them.
I know front press is better builder for shoulders and triceps. But - back press is comfortable more for me and it is greater pectoral excercise. On top of that, I could check my good posture with that excercise more (desk job posture), as I feel that variation behind back force me to have shoulders in good, not-rounded position. And I feel that my back is also worked in that excercise in good way.
Reason I don´t do Front press so much is simple: there´s a huge list of excercise that target shoulders/triceps as a main muscles with expanders. Front press is great excercise, but for me is another excercise in "that which worked shoulder and triceps mainly list".