both are very different. personally i prefer Staniel Cay, the bar is great, nice atmosphere, friendly people, etc... on the downside, the docks are exposed to the W-NW which can be an issue once in a while in winter.
Sampson is very different. the lagoon is great with a maze of sandbars (although you can dinghy there from Staniel) and the entire marina complex is more "manicured". The restaurant is ok but very "cold", the staff isn't as friendly as Staniel... rules posted everywhere, etc... I once got to the office at 4:57 to buy some beer, they were about to close the door and refused to help...
if you want laid back, Staniel is best, if you want "fancy" then Sampson has an edge.
and while dockage is reasonable at Sampson (more of less the same as Staniel), beware of sticker shock on your metered power! runs $160 to $190 a day for a 70 footer!
no issue with your draft at either, Sampson has at least 8 MLW on approach and dockside, Staniel has 6 1/2 to 7 on approach in one spot and 10' to 12' dockside.