The glass ones I use as thick, and do NOT break easily. Like @Tor, they are easier to keep clean. Forget those little funnels. Especially with VG and the slowness.I never used glass, all my cylinders are plastic. Partly because they were cheaper and partly because they wouldn't break if you knock them over. It takes a long time for the thick liquid to pour out of a cylinder, it sticks to the sides. If I need 90mls of base for a mix I just put 92mls in the cylinder and hope it balances out. Using the 10ml for flavorings isn't too bad because it is mostly PG and runs faster. Always wondered if the liquid would pour more easily from glass.
I don't use funnels anymore because of how slowly the liquid ran through them. With the plastic funnels the tip part was tapered, you could cut off most of the tip and they would run a little faster.
I don't care for the "dropper" on the glass, though. Too thick for some tanks. Makes a mess.