I recently purchased some double-convex Yunzi stones from Yellow Mountain Imports and I've been quite happy with them. I used glass stones at my old go club in middle school and, because they were the first kind of go stone I ever played with, those are always my baseline for what stones are like.
I would agree that Yunzi and glass are similar, but there are some differences.
1. I like the sound a lot better. The sound they make moving in the bowl. The sound of the stones on the board. It seems more full than glass stones. (I'd like it if my computer had a better mic so I could share the sound with you, but it just doesn't sound right when recorded and played back.)
2. They seem to be about the same weight as glass stones - perhaps a bit heavier, but if so not much.
3. They feel softer than glass, but they also feel less fragile. This is a bit hard to describe, but perhaps the best analogy is the difference between a hardcover and softcover book. The hardcover book's cover has a bit more give when squeezed so it seems softer, but you can tell it is firmer than the paperback. (The stones obviously have no give when you squeeze them, but that's the analogy I could think of)
4. They look similar to glass at first glance, but they look different when you see them close up. Both black and white stones have a bit more of a matte finish to them (the glass stones I used did too, but these are more matte).
5. And of course the green coloration thing is awesome - I know it's not really a factor when playing, but it's pretty cool.
I had a hard time finding good pictures for the stones when I was looking around, but Wikipedia has a pretty good picture of Yunzi stones. Yunzi stone picture This is exactly what mine look like. One thing I note is that the black stones make even the tiniest speck of dust visible. I actually kind of like that about them.
None of my stones were chipped when I got them, but I've only purchased a set once so I don't know if that is always the case. The glass sets I've used always had a chipped stone or two and I know I didn't like how sharp the edge of the glass was or how glossy the broken area looked. I could chip some stones to compare, but I have no intention of doing that on purpose.
I can compare these to glass stones, but I've never used ceramic so I can't make that comparison. They are honestly similar to glass so if you really like ceramic then you may want to go with that.