Based on the price as I write, ignoring the USD to AUD conversion
S32 - Price $4.37
Dividend USD$0.087
Dividend % 1.99
AWC - Price $2.05
Dividend USD$0.028
Dividend %1.36
It looks like S32 has better growth, so I suppose it partially depends on whether you want a pure play Aluminium/Bauxite/Alumina play in your portfolio.