You are talking about top N-S?
Feet or knees is fine as long as you have a wide base.
For control, it also makes no difference if you have "one arm in and one arm out", both in, both out, etc... so long as you have your hands (or your forearms) under both of their triceps.
I feel that this is one of those positions where you can actually stay rigid, and have faith that it is physically impossible for them to turn into you to escape so long as you stay rigid (similar to a proper scarf hold or S-mount).
One in, one out is convenient for chokes. I would prefer both arms out to start setting up a N-S kimura/arm bar..
I'm sure others can give more insight, but I don't see both arms in (if I'm visualizing correctly what you're saying) as being particularly useful for either control or offense.