Gas water heaters typically last longer, cost less to operate, and produce more hot water than electric ones. As far as longevity, have the installer place a jumper wire between the hot and cold water lines where they come out of the wall. This sometimes increases the life of the water heater, regardless of whether it is gas or electric. The difference between a 50 gallon and 80 gallon water heater is 30 gallons, period. Everything else is exactly the same in both of them so if you think getting 30 more gallons of hot water during a single use is worth the money then spend it. With gas heaters there is a big difference between a 50 gallon and 75 gallon water heater.