Both products are good. We use them both. We use the Hydrazzo a lot more.

Any type of plaster is weather dependent.

Yes, there is a delay in getting products as they cannot keep up with the demand and some material components used in their product is not readily available.

The Hydrazzo is a 2 day process. The day after application, the surface is exposed and polished providing a smooth finish. It's a premium plaster finish.

The Sun Stone is a different finish, but a quality material.

The surface temperature of the pool must be 50 degrees or above to apply.

I'm not sure where you are located and if you close your pool for the winter, but the pool should remain open for 30 days after plastering. This is ensure it is properly cured prior to closing and also the water chemistry was properly balanced and stable.

I would maintain the water temperature at 70 degrees prior to closing.

Not someone who owns a pool here but they both look nice, and if you want to be done with this company ASAP I would just go with whatever makes the process go faster (ask for a discount for picking the other option since they didn’t let you know ahead of time and let them know you will be leaving a review for their company if they don’t discount basically, which you should do anyway!) also for a peace of mind call the manufacturer of the product you want and ask them if what the company is suggestion true. I have had to do this a few times during my renovation and it really helps put our contractor in check.