Glass is, in my opinion, a superior material overall. It can be used for temperature play. It can last a lifetime if cared for properly. It can be totally sanitized. And it's pretty. But it's really a matter of personal preference.
I am about to find out. I've had plastic in the past and ordered my first glass dildo today. I will try to remember to post when i can compare. I'm not a huge fan of plastic so I hope that glass is better...super stoked for some temperature play