When replacing a water heater. Am I suppose to purchase a pan from Lowes or Home Depot for a new installation. Also, should this pan be made out of plastic or metal. I have seen new installs without pans, and with pans. Also, the pan sits directly under the water heater with no gap or air space.

Also, are the two best rated water heaters for general residential use - RHeem and Bradford White.
Also, since GE is made by Rheem, this is okay too.

Thanks for any advice.