I know drywall, but do they hold up in a high humidity environment? I mean would it require more maintenance than a block wall.
High humidity isn't the problem -- wetness is. Drywall is as maintenance free as blocks are until Murphy shows up.
If you have the means to get the tools, I would go with PEX rather than anything else available.
If you can post on DR1, you too could install PEX -- it is just that easy!