[cogman10]

I believe stainless steel has a slight anti-microbial property not present in glass.

Either way, both are far better than plastic. Plastic has no such anti-microbial effect AND tends to scratch from cleaning which makes wonderful footholds for bacteria. Further, because plastic is a hydrocarbon it is a potential food source for bacteria and fungus.

Even if the bacteria/fungus is harmless, you are looking at ingesting a bunch of plastic as it starts to degrade.