What model Gas Bradford White to use?

[DL]

Remodeling whole inside of house, just like new construction.

Whats the scoop on these?

DEFENDER SAFETY SYSTEM® EXTRA RECOVERY
ATMOSPHERIC VENT ENERGY SAVER MODELS

M-2-XR65T6FBN 65 gallon

M-2-XR504T6FBN 50 gallon

Have a New Sundance Optima Spa on back screened in porch. I have ran a cold water and a hot water spicket on back wall for filling Spa, Added Hot Water tap in case I want to speed up temperature of water when filling.

Thanks for your help,