It depends on what you need them for.

Glass can be easily sterilized, making it a great toy for sharing and group situations. Depending on the shape, it can also be used anally, or vaginally since it can be sterilized.

Overall, glass is very versatile. The weight is also something different. Just leaving a glass toy in while clitorally masturbating can be an experience as well.

Glass is very firm (great for P or G spotting) and smooth. It comes in a variety of textures and shapes and won't dry up lube or your natural moisture like silicone. It's extremely safe, sterilizable (so it's shareable), compatible with all lubes, and hypo-allergenic. Glass toys are made of boroscillate (Pyrex) glass which is very safe, difficult to chip or break and won't shatter into tiny pieces (it's not like drinking glasses or window panes). Contrary to popular fears, glass dildos won't break inside you. They are heavy, which is sometimes a pro and sometimes a con depending on how it affects your use. Glass toys are also beautiful and many look very artsy, come in a wide variety of colors and designs, with lots of artistic techniques used in their design to create lots of different and unique designs, and some don't even look like sex toys at all!

I love my glass dildo. the heaviness and firmess of it makes it the only reliable g-spot orgasm I can have (without a partner). It also looks so darn sexy! They are usually very reasonably priced too (not to mention safety as mentioned above!).

I want to try glass next--all I hear is how awesome they are, and well, I like awesome things--especially if I can masturbate with them.

Weight! I like to insert weighted toys and pull them with my muscles (do kegels). Do this with a clitoral vibe! BLISS!