Because glass is an insulator, it takes longer to heat up, but then stays at the temprature longer. Metal heats up quicker but also doesn't stay warm for as long a time. Here are several interesting links that are helpful for deciding what to pick for each situation.
chow.com: Rushing says glass is best for foods like cakes, which
bake for a relatively long time at lower temperatures. As in a thick
cast iron pan, cornbread baked in glass will brown more evenly than if
you use a thin metal dish. However, glass bakeware cannot be made in
large sizes and is generally unavailable with a nonstick
coating—Teflon is very hard to apply to glass. Other disadvantages of
glass are that it is more expensive and much heavier than metal, and
it can shatter if its temperature changes too quickly.
yumsugar.com: According to Lauren Chattman, author of The Baking
Answer Book, clear glass, much like dark metal, absorbs heat, making
it ideal for crisp-crusted pies but much less so for bar cookies,
quick breads, and fruit crisps, which can easily become burnt.