Titan X vs Titan Z for fluid simulation

I am developing a particle based fluid simulation application with CUDA. Now I am deciding between Titan X and Titan Z.(Price is no issue) I know Titan X is newer with Maxwell. But Titan Z is dual-core. Is there any modification you should make to your current code to make them dual-core compatible? Does dual-gpu card works as if there is only one gpu but has twice cuda cores? Thanks in advance