Which one is better, using a glass cup and washing it or using a plastic cup and recycling it?

In my house we would like to think we are pretty eco friendly. We recycle the most on our block and and use flourescent light bulbs among other things. We also use both glass and plastic cups (which we recycle). Now I know the slogan recycle reduce reuse and we recycle the plastic and reuse the glass but which one is better. I know that with the glass we are using water and with the plastic we use so many so me and my aunt have been pondering this question for awhile. Is it better to use recyclable cups or reusable cups?