I do the primary fermentation in a plastic bucket then rack to a glass carboy for secondary fermentation. Once secondary fermentation/lagering is complete I drop the temperature of my fermenting fridge which drops all the yeast to the bottom and clears the beer very well, then rack to kegs.
datfrog
the advantage of glass is that when in the secondary for an exented period of time the surface area is very small and reduces the chance of oxidation. I find it is also great to be able to see what is going on with the beer, it is very easy to see how the yeast is going.
Hoops