Most of the time, either type of pan will give you good results. But there are slight differences because of the way each
conducts heat. Here's how they affect brownies.
If you like fudgy brownies, a glass pan is best. It heats more slowly, so the batter takes a while to heat. Once it gets hot,
glass holds in the heat, cooking the brownies around the edges faster while the middle stays fudgy. The heat continues to
build in the pan the longer it's in the oven—keep a close eye toward the end of baking to prevent overdone (or even burned)
If you like less-fudgy brownies with crispy edges, go for a dark metal pan. Metal heats up quickly and is noninsulating, so
the heat transfers faster and more directly to the batter for more evenly done brownies. Darker metal or metal with a
nonstick coating is best at conducting heat—and crisping the edges where the batter touches the pan. Lighter-colored shiny or
matte metals heat slower and create a less-crispy edge.It's also important to note: because they can shatter, glass pans
should never be placed over direct heat or under the broiler. And aluminum and cast-iron pans can react with acidic food(s),
such as most fruit. So stick to glass, ceramic or coated-metal pans if baking desserts like fruit cobbler.
Finally, age-old recipe-writing convention is when a recipe calls for a "baking dish," that's code for a glass or ceramic
dish. When a "baking pan" is specified, that means metal. For the best results, stick with the type of dish (or pan) called
for in the recipe.