I want to begin with proclaiming I prefer a glass pipe over a metal pipe any hour of the day. First, a glass pipe will not get as hot as quickly as a metal pipe does. It does get hot, not as hot. Second, resin doesn't stick to the glass as much as it sticks to metal. Yes, a metal pipe is easier to get to the inside because it comes apart. But if you buy the right glass pipe where the carb and the toke n' choke hole line up right for cleaning, its simple. If not your stuck boiling it and still find yourself restling with the now loose an wet resin. Third, a glass pipe is far more fragile than a metal one. Metal ones are built to least. Gass pipes, even the thickest, risk the chance of breaking. Of course the thicker ones are more sturdy and are more apt to survive a drop, but they will break eventually. I have had glass pipes last me for years before it broke. Usually it's because someone else dropped it in the right angle and on the right surface. The hits are much cleaner tasting on a glass pipe.
When you decide to purchase a glass pipe, go for the most functional, not the coolest looking. As mentioned above, you want to be able to clean it easy, so get one where the carb is workable. Pay attention the bowl size; Get a size that fits your needs; Get a thicker glass pipe; Make sure its long enough to not burn your nose hairs when you go and lite it.