I am considering a pool and the finish options are quartz vs pebble.

I am familiar with plaster and pebble.

Does anyone have the quartz finish, I am particularly interested in cleaning / staining. I have heard it takes, and retains a stain worse than pebble. But that came from a guy trying to sell me the pebble finish as an upgrade.

Refinished ours with Pebble, it's held up well, if you do pebble get the small pebble finish, easier on your feet. Quartz is just another aggregate finish type, it really depends on the look you are after.

All the aggregate type finishes will outlast the standard type

Replaced the standard finish after 20 years as it was deteriorating.

Some light reading.
https://poolonomics.com/pool-finishes/

I've got pebble and recommend it highly.

We got the pebble at our last house, no complaints except the color. The wife picked a more green than blue color and I didn't like the way it looked.

I learned after that and after some granite counter tops we had done that she is color blind. I do the colors now

just re-did my pool with the mini-pebble finish - much easier on the feet than the pebbletech finish