I use a plastic bowl with microban.
it gets put in the dishwasher every night and then I wash it by hand in the morning(to get off dish soap residue) I use lemon water and vinegar and a soft sponge
I have used stainless steel bowls but mine will not drink water out of stainless steel and they will not eat wet food out of stainless steel.
between the microban and the heavy washing i feel fine about my plastic bowls
hear is some info on microban if you want to learn a little more
Microban Antimicrobial Product Protection