Re up vs down:
Galley down in many ways is more like a typical monohull
galley. Most folks prefer galley up for several reasons (generally the inverse of why they don't like galley down).
Social. Those cooking
are not isolated down in the hull
. Inversely with a galley down you can work uninterrupted and don't have galley mess essentially in the main salon
Stability Underway. A galley up, depending a bit design, is closer to the meta-center of the boat and thus has less motion than one further outboard
in a hull
View/Sea sickness. Galley up typically has a good all round view and most are less prone to get sea sick while working in the galley.
Ventilation. Galley ups are typically better ventilated.
Traffic flow. Most galley downs are mid ships so you have to pass thru the galley going fore and aft. Galley ups typically don't obstruct traffic flow thru the boat.